International Journal of Modern Physics B

Microstructure and tensile properties of squeeze cast Mg-Al-Ca alloys with different levels of calcium addition (AMC50X) were studied. The microstructural analysis by optical and scanning electron microscopy (SEM) shows that the squzeeze cast Mg-Al-Ca alloys contain primary α-Mg, (Al, Mg)₂Ca and Mn-Al intermetallic while the base alloy AM50 contains primary α-Mg, β-Mg₁₂Al₁₇ and Mn-Al intermetallic. The addition of calcium varying from 1 to 4 wt.% increases the fraction area of Ca-containing secondary phases from 9.5% to 19.5%. The experimental observation confirms also that the calcium has a grain refining effect on the base alloy AM50A. The tensile testing results indicate that, as the calcium content of AMC50X alloys increases from 0 to 4%, the ultimate tensile strength (UTS) and elongation (E_f) decrease dramatically at room temperature as their yield strengths (YS) improves slightly. At 150°C, however, both the UTS and YS of the alloys increase with increasing the Ca content.

One kind of meta-stable β titanium alloy with grain sizes less than 1µm was developed using conventional plastic deformation process in Northwest Institute for Nonferrous Metal Research (NIN). The so called Ti-B19 alloy (Ti-Al-Mo-V-Cr-Zr) possesses excellent strength and toughness. In order to excavate the potential workability of the alloy, isothermal compression tests were carried out on the Gleeble-1500 thermal simulator at the temperature from 750°C to 1000°C and strain rate from 0.001 s^-1 to 10s^-1. The results indicate that the flow stresses of the alloy will be heavily influenced by the strain rates and deformation temperature. The flow stress decrease with the increase of deformation temperature, and increase with the increment of strain rates. A constitutive equation for the flow stress has been defined and the test conditions for a homogeneous deformation evaluated, and the material constants including activation energy Q, stress exponent n and constant ln (A) were also obtained.

Alloys in the dilute Ti-Al-Mn system, which are considered to be near-α alloys, possess an attractive combination of strength and ductility, with the room temperature properties being intermediate between CP Ti and Ti-6Al-4V. Low levels of Fe are often tolerated in such alloys, but rarely introduced as deliberate alloying additions (with the exception of CP Ti grades), and from a processing perspective, it may indeed be desirable to have higher tolerances for Fe as it is often a common contaminant which must be controlled. In this presentation, the effect of 0.3wt.%Fe on the microstructure and behavior of a Ti-0.75wt.%Al-0.75wt.%Mn is reported. It was found that annealing in the (α+β) phase field can lead to an increase in the ductility of the alloy without having a detrimental effect on the tensile strength.

Silicon nitride bonded silicon carbide (Si₃N₄-SiC) refractories are commonly used as the sidewall of aluminum electrolysis cells. They have to withstand an extremely corrosive molten electrolyte bath for long periods. The sidewall is normally protected with a layer of solidified electrolyte (called frozen ledge), which is sensitive to the thermal conductivity of the sidewall. In this work, through review of the literature on modeling methods for predicting the effective thermal conductivity of dense composites and porous materials, some selected methods were applied to calculate the effective thermal conductivity of Si₃N₄-SiC refractories. The model predictions were compared with the thermal conductivity of a commercial Si₃N₄-SiC refractory measured by using laser flash technique. The present study showed that, due to multi-phase nature and complex microstructure of Si₃N₄-SiC refractories, most of the selected modeling methods individually do not give satisfactory predictions in one step. Recursive applications of one method or combinations of different methods are capable of giving satisfactory predictions.

The effects of Y addition up to 5.13% (in weight) to Mg-Zn-Zr alloys on oxidation behaviors under atmospheric ambient conditions were investigated in this study. Samples were heated in the ambient atmosphere at 400°C, with samples cooled to room temperature for mass measurement after some period time of cumulative exposure to obtain kinetic curves. XRD is used to analyze the mixture of oxides. Scanning electron microscopy combined with energy dispersive spectroscopy was used to study the scale microstructure and to obtain composition-depth profiles through the oxide layers. The oxidation results show that the weight gains for the alloys containing low Y concentration are obvious. The oxide films are thick and porous on the alloys containing low Y and thin and protective on alloys containing relatively high Y concentration. The addition of Y into Mg-Zn-Zr alloys results in the formation of protective film which is resistant to oxidation.

This paper describes the application of a new in-cavity thermal measurement method to determine the heat flux and calculate heat losses during high pressure die casting of aluminium A380 alloy and the magnesium alloy AZ91-D. Thermal management of the die is a critical concern in high pressure die casting and the development of microstructures after solidification. Detailed measurements were performed using infra-red probes linked to pyrometric chains and thermocouple arrays that accurately determine both casting and die surface temperatures enabling the determination of heat flux densities and interfacial heat transfer coefficients and the rapid evolution of these values with time during high pressure die casting of these alloys. The energy losses during the spray cycle can then be determined by integrating the heat flux curves for the duration of the spray application. The significance of the findings presented in this investigation arise from the uniqueness of the measurement methods applied to the determination of heat flux during the high pressure die casting of both magnesium and aluminium alloys. In particular the detailed knowledge of the thermal characteristics occurring at the cavity fill stages of the die casting process achieved through the selection of an array of fine rapid-response thermocouples integrated in one sensor along with the light pipe/pyrometric chain have enabled the accurate measurement of both the die and metal surface temperatures through the entire die casting cycle enabling the calculation of heat losses during solidification and processing.

Hot workability of Ti-6Al-4V alloy with different initial microstructures was investigated by considering processing maps and the dynamic material deformation behavior. The emphasis has been focused on the effect of initial microstructure (equiaxed versus bimodal structure). Process maps were generated using the dynamic material model (DMM), unifying the relationships between constitutive deformation behavior, hot workability and microstructures evolution. Also, the flow instability was investigated using the various flow instability criteria and microstructural analysis. To establish the processing maps with different initial microstructures, high temperature compression tests were carried out at various temperatures and strain rates up to a true strain of 0.7. Microstructural changes occurring during the deformation were analyzed in terms of high temperature deformation mechanisms. Finally the useful instability criterion for predicting the forming defects was suggested through the compression test results with different temperatures and strain rates.

The effects of carbon and oxygen additions on the microstructure and mechanical properties of a new type low-cost beta titanium alloy Ti-4.3Fe-7.1Cr-3Al have been studied. The results showed that with the carbon addition the grain size was refined significantly, followed by the tensile strength increase and ductility improvement. At 0.2 wt.% carbon addition the 0.2%YS increased by 22% and elongation increased to a peak value of 23%. Also with the carbon addition the oxygen content in the alloy could be allowed to reach 0.2wt.% without tensile property decrease. After ageing treatment, it was found that ageing temperature other than carbon content played a key role on the α-phase precipitation and ageing hardness. The hot-rolling deformation accelerated the ageing response. The optimal ageing process was decided to be 500°C for 1h under the pretreatment of 850°C hot-rolling followed by immediately water quenching. The reasons for these improvements were discussed in terms of the carbide pinning and α-phase precipitation.

It is well-known that the plasticity of magnesium and magnesium alloy is too low to be processed at low temperature. After normal hot extrusion, the plasticity of magnesium alloy can be improved, but not noticeably. In this paper, cold extrusion of commercial AZ31 magnesium alloy with severe plastic deformation was performed at room temperature with various extrusion ratios from 2:1 to 12.5:1 in order to refine the grain size of AZ31 magnesium alloy. Finally the grain size between 2~3 µm was obtained. And the influence of different grain size on the plasticity was further investigated. And the elongation of the initial billet with the grain size of 300 µm whose elongation is about 10.4%. After extrusion at room temperature with different extrusion ratios, the average grain size can be refined to below 10 µm, and the plasticity increased to 24%~30%. In order to study the effect of plasticity of AZ31 magnesium alloy under different processing techniques, we study the correspondence between plasticity and crystalline size at the same time. All results proved that, the increase in elongation could be mainly attributed to refining of the grain size of the magnesium crystalline. It also showed that, when the average grain size of AZ31 magnesium alloy was below 5 µm, the plasticity increased noticeably by cold extrusion.

This study demonstrates and explains the effect of strontium modification on machinability of aluminium-silicon eutectic (LM-6 type) alloy. This alloy is known to have many favourable features including weight to strength ratio, high corrosion resistance and excellent castability. However, normal unmodified LM-6 alloy has poor machinability, which reduces its applications range. In this work, various samples of LM-6 alloy were cast using sand and metallic chill mould with and without strontium addition. Machining on each cast product, was carried out using recommended cutting parameters for Al-Si alloys. Strontium modified samples have recorded a reduction in average flank wear, an increase in shear plane angles and a reduction in chip thickness. The main reason for this improvement is the refining effect of strontium, which reduces the size of the hard silicon particles. As a result, their abrasive action on the tool face has reduced a lot. Dramatic reductions in tool wear rate were recorded when the microstructures were refined. On the other hand, when no refinement of microstructure occurs, tool wear rate becomes high. Chip analysis showed that strontium modified sample produced a thinner chip thickness with a larger shear plane angle, requiring less cutting forces. The tool wear depends not only on the phases present in the work material, but also on their sizes and distribution over entire structure. Thus, strontium modification has better effect on machinability of die cast alloy compared to that of the sand cast LM-6 alloy.

An aim of the experiments is to study alloying techniques of dollop-like MM, as-cast and extruded Mg-MM master alloy in die casting AZ91D magnesium alloy at conventional cold chamber die casting temperature. The as-cast AZ91D-1.2wt%MM alloys were prepared and MM was added by different way at 720°C. The results showed that the efficiency of alloying achieved less than 50% within 30 min when dollop-like MM was added. When MM was added by as-cast and extruded Mg-21wt%MM master alloy, the efficiency of alloying was improved significantly. The microstructure and analytical studies were carried out using optical microscopy and differential scanning calrimetry (DSC). Testing results showed the Mg-MM master alloy could melt easily down at die casting temperature because Mg-RE phases with lower melting point were formed. The grain refining efficiency of the master alloy was improved by extrusion. The improvement could be attributed to the decrease in Mg-RE particle size and increase in the number of nucleating sizes for Mg. Then die-casting AZ91D-0.44wt%MM test bars were produced with addition of extruded Mg-21wt%MM master alloy and the efficiency of alloying was around 80%.

The electrochemical deposition of magnesium was investigated in ethereal Grignard salt solution with tetraethylammonium bistrifluoro-methanesulfonimidate additive, using cyclic voltammetry, potentiostatic transients, and scanning electron microscope measurements. The voltammograms showed the presence of reduction and oxidation peaks associated with the deposition and dissolution of magnesium. From the analysis of the experimental current transients, it was shown that the magnesium deposition process was characterized as a three-dimensional nucleation. The deposited product obtained from potentiostatic reduction presented a generally uniform and dense film.

The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al-Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al-Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al-Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF₆) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al-Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions.

The effects of different isothermal holding temperatures and times on the morphology of Chinese script shaped or fibriform eutectic Mg₂Si phases in a Mg-3Si-3Sn alloy were investigated during isothermal heat treatment. With increasing heat treatment temperature, the spheroidizing time for the coarse eutectic Mg₂Si phases is reduced dramatically. After isothermal heat treatment of 2 h at 550°C, the morphology of the eutectic Mg₂Si transforms completely from the coarse Chinese script type and fibriform shape into fine, spherical shape with the lowest interface energies. The spheroidizing mechanism of the Chinese script shaped or fibriform eutectic Mg₂Si particles seems to be attributed to the 'Rayleigh shape instability'.

The microstructural evolution in an Al-Cu-Mg-Ag alloy with trace Zr addition during homogenization treatment was characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDS). It was shown that the low-melting-point phase segregating toward grain boundaries is Al₂Cu, with a melting point of 523.52°C. A two-step homogenization process was employed to optimize the microstructure of the as-cast alloy, during which the alloy was first homogenized at a lower temperature, then at a higher temperature. After homogenized at 420°C for 6 h, Al₃Zr particles were finely formed in the matrix. After that, when the alloy was homogenized at an elevated temperature for a longer time, i.e., 515°C for 24 h, most of the precipates at the grain boundaries were removed. Furthermore, the dispersive Al₃Zr precipitates were retained, without coarsening greatly in the final homogenization step. A kinetics model is employed to predict the optimal homogenization time at a given temperature theoretically, and it confirms the result in present study, which is 420°C/6h+515°C/24h.

The kinetics and mechanism of hydrogen absorption in Ti600 alloy were investigated at various temperatures (873K ≤ T ≤ 1123K). The rate of hydrogen absorption and equilibrium hydrogen pressure increased with the increase of temperature. Because hydriding reaction is an exothermic reaction, solubility of hydrogen decreased with increasing temperature. The experiment results were interpreted from the time dependent hydrogen absorption curves using various rate equations to reveal the mechanism of the hydrogen absorption processes. The hydriding reaction rate constants were extracted from the time-dependent hydrogen absorption curves. The mechanism of hydriding reaction in different stages has been analyzed. It was found that the chemical reaction process dominated the hydrogen absorption process at 923K. The chemical reaction process and the three-dimensional diffusion process dominated the hydrogen absorption process at 973K or higher.

The modification of liquid metal by electric pulse (EP) is a novel method for grain refinement. In this work, based on the reported structural heredity of EP-modified liquid aluminum, we investigated its viscosity change by using torsional oscillation viscometer. The results validate the viscosity of EP-modified liquid aluminum also decreases with increasing temperature and meets approximately exponential correlation on the whole. Moreover, it is especially important that the EP-modified liquid aluminum has the higher viscosity and possesses the bigger viscous-flow cluster in a certain temperature range, which should be associated with the increase of the order degree of its liquid structure. Differential scanning calorimetry (DSC) measurement also confirms that viewpoint. These coupling results experimentally testify the proposed mechanism of electric pulse modification (EPM) modeled merely by postulation.

The effect of processing parameters on hot workability and microstructure evolution during subtransus deformation of TC11 alloy with widmanstăten microstructure was studied using isothermal compression tests. Testing was conducted at strain rates of 0.1-10s^-1, temperature ranges 920-980°C and height reductions of 30-70%. The influence of hot working parameters on flow behavior, hot workability and microstructure evolution was systemically investigated. The results showed that all the flow curves exhibited a peak stress at very low strains (<0.1) followed by extensive flow softening. Surface fracture, cavitations and localized shear flow were found to be main factors that limited the hot workability of TC11 alloy. At low strains, lamellar kinking started to occur due to the orientation between the colony α lamellar and stress axis. With deformation continues, reorientation of the lamellar colony occurred and the deformed lamellar became elongated and thinner. At high stains, segmentation and globularization of α lamellar took place to produce a refined microstructure with α grain size around 1 µm that is technologically desirable for secondary processes such as superplastic forming. A microstructure mechanism map based on the previous results was then established and applied to process design considering defect and microstructure control.

Experimental and microstructure simulation approaches were taken to investigate the morphological evolutions of primary particles in an Al-20wt% pct Cu alloy under LSPSF (low superheat pouring with a shear field) rheocasting conditions. The results indicate that crystals are globular and present in non-entrapped eutectic, after 3s of solidification. The morphology of these crystals during the subsequent free growth is determined by both the number of free crystals and the cooling intensity of melt. Analyzed results from microstructure simulation and two stability models suggest that the primary globular particles formed in the earlier stage of solidification can attain growth stability up to a larger size scale.

Effect of Al-Ti-B master alloy on the microstructure and mechanical properties was investigated in AZ31 magnesium alloys micro-alloyed with Ca. During the casting process, electromagnetic field was also introduced. The results suggest that the micro addition of Ca to magnesium alloy retards the oxidation rate during melting process, improves casting qualities of magnesium alloy ingots. The grain size of AZ31 magnesium alloy has been effectively reduced by optimum addition of 1 wt.% (designed composition) Al-Ti-B master alloy. In this process, the addition level of Ti is the key factor to affect grain size of magnesium alloy, in which two grain refinement mechanisms are built by both TiB₂ and residual Ti. Moreover, the electromagnetic field leads to uniform distribution of temperature field and solute field in the molten pool, increases casting qualities and refines grain size further.

Mg-5Li-5Al-3Zn-xCd(x=0,2,3,4,5) alloys were prepared. The densities of these alloys were measured with Archimedes' method. The influence of Cd element on the microstructure and the properties of these alloys were also studied. The results indicate that these alloys possess low density ranging from 1.5 to 1.7 g·cm^-3. The addition of Cd has the refining effect on the α-Mg phase and causes the formation of Mg₃Cd intermetallic compound. The refinement and the formation of Mg₃Cd improve the mechanical properties of alloys. When the Cd content is 3 wt.%, the tensile strength of alloy reaches its peak value(288 MPa).

A novel Al-7.5Zn-1.6Mg-1.4Cu-0.12Zr alloy was subjected to the retrogression and re-ageing (RRA) treatments at a lower range of retrogression temperatures from 170 to 200°C. The effect of RRA on the mechanical properties, electrical conductivity and the microstructure of the alloy has been investigated. The results indicate that an increase in the yield strength of the alloy can be achieved after RRA treatment. With increase of the retrogression temperature, the retrogression time for keeping the strength levels similar to T6 temper decreases rapidly. When submitted to RRA at 170°C for 90-120 min, the alloy can obtain a good performance on both SCC and mechanical strength; the electrical conductivity was above 40%IACS, reaching values typical for T76 condition and the tensile yield strength values were 552-570 MPa which is higher than that of the T6 temper. The microstructure is a very fine distribution of GP zones and η′ precipitates inside grains, similar to T6 condition and η precipitates on grain boundaries distributed similarly to T7 temper.

Phase Transition Cooling (PTC), using the absorbed latent heat during the melting of phase transition cooling medium to cool and solidify alloys in the process of casting, is a new casting technology. Specimens of A356 casting aluminum alloy were prepared by this method in the paper. The new heat treatment process (cast and then aging directly without solid solution) of A356 alloy was performed. For comparison, the conventional T6 heat treatment (solution and then aging treatment) was performed too. The mechanical properties of A356 alloy with different heat treatments were measured by tensile strength testing methods and microstructures of the alloy with different heat treatment process were investigated by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-rays diffraction (XRD) and transmission electron microscopy (TEM) too. The results show that ultimate tensile strength (UTS) of A356 alloy with the new heat treatment process is much higher than that with conventional heat treatment while the elongations with the two heat treatment processes are very close. This is due to the grain refinement obtained after PTC processing.

Backward tube spinning experiment of BT20 (Ti-6Al-2Zr-1Mo-1V) alloy was carried out with an aim to examine texture evolution of titanium alloy in spinning process. The initial texture and the spinning texture were investigated by X-ray diffraction, and deformation history of a single-pass spinning was analyzed using finite element method. Tilt basal texture occurs when thickness reduction reaches a medium level (~ 49% for the outer surface and ~ 58% for the inner surface in the present study) and that further deformation promotes the formation of central basal texture. During early several passes basal texture in the outer surface develops more rapidly and intensely than that in the inner surface due to much larger deformation. However, the maximum intensity of texture in the inner surface reaches a higher level in subsequent passes for the following two reasons: (1) the discrepancy between equivalent deformation in the internal layer and that in the external layer reduces with increasing deformation; (2) material in the inner surface undergoes much smaller transverse shear deformation. Spinning texture is characterized by its asymmetry, which results from asymmetric spinning deformation investigated by analyzing deformation histories of material particles located in the inner and outer surface.

Microstructural characterization of as-cast and extruded experimental alloys as (A) Mg-6.86Li-3.02Al-1.12Ce-0.7Ca (B) Mg-8.15Li-3.07Al-1.12Ce-0.72Ca (C) Mg-10.54Li-3.54Al-1.23Ce-0.94Ca are researched in this paper. The results show that the as-cast specimens of (A) and (B) are composed of α (Mg) phase, β (Li) phase, rod-like and bulk Al₂Ce compound. On the other hand, β phase (Li), bulk and rod-like Al₂Ce compound, Al²Ca compound at boundaries are observed in the as-cast (C) alloy. The addition of Ce and Ca also shows in the microstructure the presence of Al-Ce-Ca phase, a solid solution of Ca in Al2Ce compound. In the extruding alloys, the microstructure is refined and the β phase has the effect of coordination during deformation. The long rod-like and the bulk compounds become short rods and fine clumps distributing evenly in the extruding direction after extruding process. The microstructure of extruded Mg-10.54Li-3.54Al-1.23Ce-0.94Ca alloy testified the existence of eutectic structure.

Ultrafine-grain size of ~1µm was achieved in an AZ31B Mg alloy wires with high strength prepared by cold drawing and subsequent annealing in the present study. Effects of cold-drawn area reduction (CAR) on strain hardening, recrystallized grain refinement and annealing temperature were investigated. The results showed that the maximum cold area reduction as high as 65.1% could be reached at room temperature, which resulted in the notable strain hardening, grain refinement and the decrease of annealing temperature.

The dynamic recrystallization (DRX) of TA15 (Ti-6Al-2Zr-1Mo-1V) titanium alloy during the hot deformation process was studied by the Cellular Automata (CA) model which is base on the dislocation density theory. To build the CA model, the dislocation density model, dynamic recovery model, nucleation model and grain growth model were introduced and developed. The influences of strain rate on the microstructure evolution and flow stress character were investigated which shows that high strain rate leads to later DRX appearance, high flow stress peak value, small mean size of recrystallizing grains(R-grains) and low DRX percentage, but they have the similar Avrami curve. The characteristic of DRX process in a modeling non-uniform temperature filed (NTF) has been studied. All the simulation results show good agreement with the pioneer's work and experimental results.

Hydrided Mg-3Ni-2MnO₂ composite powders were prepared by mechanical milling under hydrogen atmosphere. Heat and mass transfer, the effective thermal conductivity (ETC) of the hydrided Mg-3Ni-2MnO₂ powder reaction bed with various porosities were measured using a self-made apparatus. The effect of porosity on the bed is also analysized. The results show that the ETC of reaction bed is poor and it increases with decreasing porosity. Three porosities, 0.37, 0.53, 0.63 were selected in the present work. The bed with 0.53 porosity exhibits relatively fast reaction rates in both hydrogenation and dehydrogenation process. The hydrogenation process is a fast exothermic reaction resulting in a quick increase if the temperature of the bed during this process, and there is a temperature gradient: the temperature close to the bed wall is lower but higher at the center of bed. In dehydrogenation of the bed, the temperature of hydrided bed decreases due to the endothermic reaction, and the temperature at the center falls the lowest and keep at that temperature for a long time. The analyses reveal that increase of ETC don't always helps to improve the bed's hydriding and dehydriding rates. There should be an optimal porosity which helps to transfer both the heat and the mass.

Mg-Cu-Zn ultrafine eutectic composites with different length scale heterogeneity, consisting of micrometer size dendrites and/or ultrafine scale bimodal eutectics, exhibit high yield strength as well as good plasticity at room temperature compression. Among these alloys, micron-scale α-Mg dendrites reinforced ultrafine eutectic composites exhibit high yield strength of 310 ~ 420 MPa and large plasticity of 7 ~ 12%. Meanwhile, a Mg₇₂Cu₅Zn₂₃ alloy comprising a bimodal eutectic structure without the micron-scale α-Mg dendrites shows the optimized mechanical properties the highest yield strength of 455 MPa combined with a considerable plastic strain of ~5%.

Ultrafine eutectic alloys have been developed in Ti-Ni, Ti-Fe and Ti-(Ni, Fe)-Sn alloys. The Ti₇₆Ni₂₄ and (Ti₇₄Ni₂₆)₉₇Sn₃ ultrafine eutectic alloys consist of a mixture of α-Ti and Ti₂Ni phases, and β-Ti(Sn) and Ti₂Ni phases, respectively, whereas the Ti_70.5Fe_29.5 and (Ti_70.5Fe_29.5)₉₇Sn₃ alloys are composed by a mixture of β-Ti(Sn) and FeTi phases with relatively spherical colony. The compression tests of Ti₇₆Ni₂₄, (Ti₇₄Ni₂₆)₉₇Sn₃ and Ti_70.5Fe_29.5 ultrafine eutectic alloys reveal a strength of 1400 ~ 1800 MPa with very limited plastic strain of 0.1 ~ 1%. On the contrary, a (Ti_70.5Fe_29.5)₉₇Sn₃ alloy exhibits high strength of 2270 MPa with enhanced plastic strain of 3.1%. Based on these results, it is feasible to suggest that the eutectic morphology and interfacial coherency between the Ti solid solution and intermetallic phases influence to control the macroscopic plasticity of the Ti-Ni and Ti-Fe ultrafine eutectic alloys.

Three different thickness ceramic coatings were deposited on die-cast AM50 magnesium alloy in KOH and NaAlO₂ solution using electrolytic plasma oxidation (EPO) technology for corrosion prevention. Immersion corrosion tests were carried out in 3.5% NaCl solution for 336 hours to investigate the effect of coating thicknesses on tensile and fracture behaviors of the coated AM50 alloys. The results show that the yield strength (YS) and ultimate tensile strength (UTS) of the coated AM50 alloy subjected to immersion corrosion increase with an increase in coating thicknesses. Further analyses on stress and strain curves indicate that the coating enhances the strain-hardening rates of the corroded alloy during its plastic deformation. SEM examination on the fractured surface manifests that the substrate AM50 alloys exhibit characteristics of ductile deformation with deep dimples. However, brittle features prevail on the fractured surface of the mixed layer of coating plus oxidation corrosion product. Micro cracks were observed between the mixed layer and the AM50 alloy substrate induced by corrosion and within the mixed layer induced by EPO process, which could be responsible for the brittle fracture.

Influences of Zr addition on microstructure and tensile properties at ambient and elevated temperatures have been investigated for precipitation-hardened Mg-3%Nd-0.6%Zn and Mg-3%Nd-0.6%Zn-0.2%Zr casting alloys. By the addition of Zr, the average grain size of α-(Mg) phase decreases remarkably. In T6-treated state, the Mg-3%Nd-0.6%Zn-0.2%Zr alloy shows higher YS, UTS and elongation at RT, 150°C and 200°C, compared to those of the Zr-free alloy. Better creep resistance is observed in the Zr-containing alloy at 175°C/120MPa condition, while its creep resistance becomes inferior to that of the Zr-free alloy at 215°C/80MPa and 250°C/40MPa conditions. The discrepancy between tensile and creep properties is discussed in relation to microstructural evolution.

In this study, a novel method two-step foaming method (TSFM) has been proposed to fabricate Al alloy foams with irregular shapes. The two steps Al alloy foaming process and cell-structures evolution have been investigated experimentally. The relationship between foamable precursor, foaming parameters and cell-structures of the final foam samples has been observed. Moreover, the Al foam samples with regular and irregular shapes prepared by TSFM are shown in this paper.

Corrosion behavior of the casting Al-Cu alloys with and without Sc addition was studied by both the immersion test and electrochemical measurement methods. The results show that pitting corrosion was found on the surfaces of these alloys in 3.5wt.% NaCl solution, while the corrosion resistance of the Al-Cu alloys with Sc is better than that of the Al-Cu alloy without Sc. With increasing Sc content, the corrosion resistance of the present Al-Cu alloys varies significantly, and the 0.1wt.% Sc alloy has the best corrosion resistance. Also, the corrosion potential of the present alloys with Sc is shifted positively compared with that of the alloy without Sc by electrochemical measurement, indicating that the alloys with Sc have better corrosion resistance. The microstructures of the Al-Cu alloys change from the coarse grains to the fine equiaxed grains due to Sc addition, which is responsible for the reduced susceptibility to corrosion and the enhanced corrosion resistance of the present alloys.

AZ31 magnesium alloy sheets with a thickness of about 2mm were prepared by using a unique hot rolling process which was featured by heating the rolls during rolling. Two different rolling routes were used to achieve the final thickness through 6 passes of rolling. The major rolling parameters were chosen as the same for both rolling routes except that the roll temperature was set to be 400°C for route A and the 1^st to 4^th passes of route B, but lowered to 350°C for the 5^th and 6^th passes of route B. The microstructure and mechanical properties of the alloy sheets were comparatively investigated. The results showed that dynamic recrystallization occurred during hot rolling, and by choosing the processing parameters appropriately the grain size could be refined steadily with increasing rolling passes. The final alloy sheet prepared by 6 passes of rolling via the rolling route B was featured by a very fine microstructure, with the grain size being 5μm in average. Correspondingly, it presented very high strength and tensile elongation, with its yield strength and tensile elongation achieving 206MPa and 26.4% in the transverse, and 196MPa and 27.6% in the rolling direction, respectively.

This paper describes the effect of hot extrusion on the microstructure and mechanical properties of electromagnetic continuous cast (EMC) AZ31 alloy. The microstructure, mechanical properties and fracture surfaces of AZ31 alloy before and after extrusion were investigated. The results demonstrate that extrusion processing gives rise to a strong basal texture. The grains are significantly refined and the average grain size of localized fine grain area is 2μm. Compared with EMC ingots, as-extruded specimens have much finer grain size and more uniform microstructure, and the second phase (Mg₁₇Al₁₂) becomes smaller and distributes more uniformly. The mechanical properties of the deformed AZ31 were improved after hot-extrusion. When the extrusion ratio was 10, the yield strength, ultimate tensile strength and reduction in cross-sectional area of as-extruded AZ31 alloy were 248MPa, 306MPa and 28.44%, which were respectively enhanced by 78.4%, 41% and 45.25%, compared with those of as-cast samples. With the increase of extrusion ratio, the grain refining effect was more significant and the microstructure was more uniform. The yield strength, ultimate tensile strength and reduction in cross-sectional area increased obviously with increasing the extrusion ratio. The observation on fracture surfaces demonstrates that the fracture mode changes from ductile-brittle fracture to ductile fracture after extrusion.

As-cast ZK60 magnesium alloy that has been treated by homogenizing was forward extruded at 380°C and different extrusion ratios. Half of the extruded samples were treated by T5 treatment (10 hours at 170°C). The microstructure and mechanical properties of extruded samples that have been treated by T5 treatment and not been treated by T5 treatment have been measured. Experimental results show that the T5 treatment of extruded ZK60 magnesium alloy will cause the tensile strength and hardness to increase in some sort, the yield strength to increase obviously, but elongation to decrease slightly. When ZK60 magnesium alloy is extruded at 380°C, the second phase, MgZn and a small quantity of MnZn₂, will precipitate, and the distribution of second phase is even and dispersed. After T5 treatment, the change of grain size is not obvious, but the quantity of precipitated phase obviously increases comparing with extruded samples, and some of the precipitated phase aggregate and grow.

An inverse template method that relies on the use of a controlled porous spacer material was implemented to produce periodic magnesium (Mg) foams. Bulk infiltration pressures were varied to determine a processing-property map. The microstructure and mechanical properties of the resulting periodic Mg foams were investigated using optical and scanning electron microscopy (SEM), and compression testing, respectively. SEM was also used to analyze the surface topology of the periodic foams and compare it to the original template material. It was found that the casting pressure has a great effect not only on the success of the infiltration but also the surface roughness and other microstructural features of the foam.

Ti-43Al-9V-Y alloy billets was prepared by the quasi-isothermal canned forging processing, and effect of heat treatment processes on the microstructure of as-forged Ti-43Al-9V-Y alloy was investigated. The results show that, as-forged Ti-43Al-9V-Y alloy has streamline microstructure including a large number of recrystallized grains and broken lamellae, and different heat treatment processes were employed to obtain different microstructures of Ti-43Al-9V-Y alloy. After heat treatment at 1250°C, the microstructure of as-forged Ti-43Al-9V-Y alloy becomes γ+B2 microstructure. Comparing with the microstructure after HT of 1250°C/30 min, the precipitation of B2 lath phase in γ equiaxed grains increased and γ grains refined after HT of 1280°C/30min or 1320°C/30min. However, after the heat treatment of 1300°C/30 min, the duplex microstructures can be gained.

Nanostructured alumina ceramic templates have been fabricated by anodizing annealed high-purity aluminium foil. Pore diameter, pore separation and thickness in these alumina ceramics can be controlled using a range of acid electrolytes and anodizing voltage profiles. Thermal development of the structure of these robust and optically clear templates have been compared using XRD, thermal analysis and ²⁷Al MAS NMR techniques, showing that species substituted in the alumina lattice from decomposition of the acid electrolyte play a major role in determining the chemical and physical stability of the ceramic template at elevated temperatures. Deposition of ultrathin palladium films on the surface of these alumina templates creates robust membranes that enable hydrogen separation from mixed gas streams at elevated temperatures. Gas permeability measurements through these membranes as a function of temperature have demonstrated their very high selectivity for hydrogen.

Effects of V₂O₅ addition on the microwave dielectric properties of 16CaO-9Li₂O-12Sm₂O₃-63TiO₂ (abbreviated CLST) ceramics prepared by conventional mixed oxides method were investigated as a function of V₂O₅ content and sintering temperature. All the specimens were sintered between 1100°C and 1250°C. The sintering temperature of the CLST ceramics was lowered by 100°C with V₂O₅ addition. With the changing content of V₂O₅, the dielectric constants lie between 88.6 and 108.2, while the Q×f values are between 3275 and 6573 GHz. Especially, the specimens doped by 0.75 wt% V₂O₅ sintered at 1200°C and 1250°C for 3 h show good microwave dielectric properties with Kr=100.4-108.2, Q×f>4500GHz, and TCF=7-8 ppm/°C. Obviously, V₂O₅ could be used as a suitable sintering aid that could improve densification and microwave dielectric properties of the CLST ceramics.

We discovered that Sr₂MgSi₂O₇:Eu phosphor emits blue light under the application of a mechanical stress, a phenomenon known as mechanoluminescence (ML). The ML showed a similar spectrum as photoluminescence (PL), which indicated that ML is emitted from the same center of Eu²⁺ ions as PL. The analysis of structure and thermoluminescne suggested that the origin of ML for Sr₂MgSi₂O₇:Eu phosphor can be attributed to strain-induced electroluminescence, that is, piezoelectricity impelled the trapped electrons to escape from the trap and produce ML. Furthermore, the relation between ML intensity and compressive load is close to linearity, which indicate that this sample can be used for smart-skin and self-diagnosis applications.

A slurry immersion technique of alumina coatings was carried out on several AISI 316 L stainless steels using two types of binding agents; commercial starch and Sarawakian starch (sago), which were also mixed with polyvinylchloride (PVA) for strengthening purposes. The sintering temperatures in this work were varied from 500 to 1000°C. Prior to sintering process, all stainless steels were metallographically ground and polished to approximately 0.6 µm of average roughness. Detailed characterisations on the sintered specimens were carried out with the aid of the secondary electron microscopy (SEM), microhardness and a profilometer. The results revealed that coated steels using sago binder showed improved adhesion and homogenous microstructures with greater hardness of 2642 HV than those found in coated steel with commercial starch after sintering process.

The effect of strain rate and temperature on the mechanical behavior of the Ni-18Si-3.0Nb-1.0Cr-0.2B alloy was investigated by atmosphere-controlled tensile testing in vacuum and air atmosphere at different strain rates and different temperatures. The results reveal that the Ni-18Si-3.0Nb-1.0Cr-0.2B alloy exhibits ductile mechanical behavior (UTS > 1200 MPa, ε > 8%) at room temperature under different atmosphere conditions. In addition, both of the ultimate tensile strength and elongation exhibit quite insensitive response with respect to the loading strain rate when tests are held at temperatures below 973K. The elongation of the samples tested in vacuum and air for the Ni-18Si-3Nb-1Cr-0.2B alloy exhibits a significantly increase with temperature from 973K to 1073K. In addition, all fracture surfaces tested at 1073K in vacuum and air atmosphere presents a typical ductile fracture surface, a fully dimpled fracture pattern. The fact of increasing in elongation at high temperature (1073K) is suggested to be attributed by the dynamic recrystallization that occurs preferentially around the dispersion phase or grain boundaries and so as to enhance the ductility by reducing the stress concentration at or near grain boundaries.

The micro-pores with size of 0.2 to 1.8 µm, which randomly distribute in a 316L stainless steel substrate, were fabricated by the transfer of the porous structure of anodic porous alumina. The mask anodic porous alumina was directly prepared by anodizing of aluminum film, which was deposited on 316L substrate by DC magnetron sputtering. The transfer of the porous structure of anodic alumina into the 316L substrate could be achieved without the additional through-hole treatment to the barrier layer. The localized priority dissolution on porous alumina is observed during the anodizing. And this process is considered to lead to the micro-pores formation on 316L substrate. In addition, the effect of anodizing time on the pores size and number on 316L substrate also was discussed.

The evolution of microstructure and mechanical properties of the Ni-25Al-27.5Fe-1.0Nb intermetallic alloy after thermal mechanical treatment (TMT) was systematically investigated by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) with electron dispersive spectrum (EDS) capability, and atmosphere-controlled tensile test at room temperature with different strain rate. The results of XRD reveals that a matrix of β' phase [(Ni, Fe) Al type ordered bcc structure] and a precipitated γ phase (Ni₃Fe fcc solid solution) co-exist in this alloy after TMT. The dendritic microstructure of the as-cast alloy was eliminated after TMT process. In parallel, a refined and homogeneous distributed lath precipitates can be obtained after annealing at 820 for 4 hr. Additionally, this alloy presents a relative high strength as well as ductile mechanical behavior (UTS~1320 MPa and ε~8%, respectively) at room temperature in air. A 30% improvement in yield strength is suggested to be contributed by the refined microstructure from the TMT. Moreover, the tensile strength and ductility of this alloy exhibit insensitive response with respect to the loading strain rate at room temperature.

Alloy composition and heat treatment are of paramount importance to determining alloy properties. Their control is of great importance for new alloy design and industrial fabrication control. A base alloy utilizing MX carbide is designed through a theory guided computational approach coupling a genetic algorithm with optimization criteria based on thermodynamic, kinetic and mechanical principles. The combined effects of 11 alloying elements (Al, C, Co, Cr, Cu, Mo, Nb, Ni, Si, Ti and V) are investigated in terms of the composition optimization criteria: the martensite start (Ms) temperature, the suppression of undesirable phases, the Cr concentration in the matrix and the potency of the precipitation strengthening contribution. The results show the concentration sensitivities of each component and also point out new potential composition domains for further strength increase. The aging temperature effect is studied and the aging temperature industrially followed is recovered.

Compared with the conventional In718 alloy, the addition of Al at the level of 1.24% and 1.50% greatly increases the precipitation of γ′ phase and the compact form of γ″/γ′/γ″ structure, which has been demonstrated in previous studies. The δ phase precipitation at the grain boundaries is noticeably suppressed. Large amount of Laves phase ((Fe, Ni, Cr)₂(Nb, Mo)), small amount of M₇C₃ carbide and σ phase ((Fe, Ni)(Cr, Mo, Nb)) are precipitated at the grain boundaries. After aging at 680°C, the grain boundary precipitates are increased significantly. Large amount needle-like σ phase is precipitated at the grain boundary in the alloy with 1.50% Al. After aging at 680°C for 1000h, the grain boundary precipitates are worsened further, but the coarsening of the compact form γ″/γ′/γ″ is lighter than the γ″ phase in the normal In718 alloy.

The tensile strength at room temperature and 680°C are increased due to Al increasing. While the tensile ductility and impact toughness of the alloy decrease significantly, and a sharp decrease has been found during the long term aging at 680°C.

The mechanism by which Al influencing the microstructure and mechanical properties of In718 alloy is to be discussed.

In this investigation, a neural network model was established to predict mechanical properties of 25CrMo48V seamless tubes. The sensitivity analysis was also performed to estimate the relative significance of each chemical composition in mechanical behavior of steel tubes. The results of this investigation show that there is a good agreement between experimental and predicted values indicating desirable validity of the model. Among those alloying elements, the elements of carbon, silicon and chromium tended to play a more important role in controlling both the yielding strength and the Charpy-V-Notch transverse impact toughness. In comparison, the impurities such as O, N, S and P have a relatively weak impact. More detailed dependences of mechanical properties on each chemical composition in isolation can be revealed using the established model. The well-trained neural network has a great potential in designing tough and ultrahigh-strength seamless tubes and modeling the on-line production parameters.

Microstructure evolution and texture formation in low carbon CSP steel were observed by means of metallgraphic, TEM, and SEM equipped with electron back scattered diffraction (EBSD) system. The influence of large particles and fine carbonitrides precipitates on recrystallization and texture formation during the annealing procedure was analyzed with Small Angle X-ray Scattering (SAXS) technique in the steel. It was found that the fine precipitates present in the steel have shown ability to stimulate recrystallization nucleation and transformation during deformation, but hard to accelerate recrystallization growth because of grain boundary pinning effects in the steel. Compared with the conventional low carbon steel, the recrystallization texture and microstructure of the CSP steel show distinct character, and thus modify the mechanical behaviour of the final products.

Nanosized zinc stannate Zn₂SnO₄ (ZTO) was synthesized via a simple hydrothermal method using sodium hydroxide NaOH as a mineralizer. Hydrothermally treated at 150, 200, and 250°C for 24 h and 48 h, the X-ray diffraction (XRD) pattern showed that highly crystalline ZTO nanostructures could be formed at 200 and 250°C. Transmission electron microscopy (TEM) images showed that ZTO nanocubes were formed at 250°C, and a sheet-like structure was found at 200°C. Raman spectra revealed that ZTO had a spinel structure and there were two Raman shift peaks at approximately 668 and 535 cm^-1, which were similar to the peaks of ZTO nanowires. Furthermore, the photocatalytic activity of the ZTO samples was assessed utilizing methylene blue (MB) under ultraviolet irradiation, and the UV-Visible light absorption spectra was investigated to interpret the relationship between photocatalytic properties and light absorptivity. The sheet-like ZTO nanostructures exhibited better photocatalytic activity due to their excellent light absorption properties.

Integrally directional solidification of an advanced Nb silicide based ultrahigh temperature alloy was conducted with the use of special ceramic crucibles. The melt temperature was 2000°C and the withdrawing rate was respectively 5, 10, 15, 30, 50, 80 and 100 µm/s. The directionally solidified microstructure was composed of primary (Nb,X)₅Si₃ rods and (Nb,Ti)ss + (Nb,X)₅Si₃ eutectic colonies (here X represents Ti and Hf elements) that distributed evenly and aligned erectly along the growth direction. The quenched solid/liquid (S/L) interfaces had the morphology of a series of protruded parallel eutectic cells along the growth direction. (Nb,Ti)ss and (Nb,X)₅Si₃ slices grew in a coupled manner in each eutectic cell, forming a typical lamellar eutectic morphology. Both the average diameter of eutectic cells and lamellar spacing in them decreased with the increase of withdrawing rates. The solidification path was that primary (Nb,X)₅Si₃ rods formed firstly and then the retained liquid around solidified into (Nb,Ti)ss + (Nb,X)₅Si₃ eutectic cells.

The principal component analysis-artificial neural network (PCA-ANN) model was developed to predict martensite transformation start temperature (Ms) of steels. Training samples were processed by principal component analysis and the number of input variables was reduced from 6 to 4, then the scores of principal components were used to establish new sample database to train the ANN model. Ms of steels were predicted by the PCA-ANN model. The predicted and measured Ms distribute along the 0-45° diagonal in the scatter diagram and the statistical errors are MSE-16.0256, MSRE-4.49% and VOF-1.97790 respectively. Comparing the prediction results of different models it is shown that the accuracy of the PCA-ANN model was the highest, which indicated that the principal component analysis was helpful to improve the prediction accuracy of ANN model.

Ni-based monocrystal superalloy with fine dendrite, precise orientation and finally elevated service performance is required as turbine blades in advanced aeroengine. In this paper, the melt superheating treatment is carried out for DD3 single crystal superalloy during directional solidification processing. The thermal gradient of solidification interface remains constant for different melt superheating temperatures with the appropriate superheating treatment regulation. It is shown that with the melt superheating temperature increased from 1500°C to 1640°C and then to 1780°C respectively, both the primary and the secondary dendrite arms are obviously refined and the dendrite segregation ratios of Mo, W and Ti are reduced while the deviation angle of (001) crystal orientation can all be controlled within 5°. The dendrite structure refinement and the crystal orientation consistence should be attributed to the melt structure change and heredity which is caused by the superheating treatment.

Grain boundary character distribution (GBCD) and triple junction character distribution (TJCD) in a 304 stainless steel cold rolled with the thickness reduction of 6% and then annealed at 1323K for 5 minutes(GBE process) were analyzed by electron back scatter diffraction (EBSD). The intergranular corrosion (IGC) resistance of various triple junctions and grain boundaries were evaluated after sensitization treatment at 1073K for 30 minutes. The results showed special TJ containing 2 or 3 CSL boundaries exhibit higher resistance to IGC than other TJs. In addition, the {411} and {221} symmetrical tilt grain boundaries (STGBs) are more resistant to intergranular corrosion for Σ9 boundaries.

In this study, SKD61 tool steel was friction stir processed (FSP) using a polycrystalline cubic boron nitride (PCBN) tool. Microstructure evolution and mechanical property in FSP zone were investigated. Microstructural observation results showed that the microstructures in FSP zone surface were fine grains in the range of 1 - 4 μm due to large plastic deformation during FSP. Micro-hardness test results showed that the average hardness value in FSP zone was 773 HV, 3.7 times the hardness in base metal (210 HV). The wear test results showed that FSP surface showed a significantly lower wear rate than that of the base material at all loads. The relation between microstructural evolution and mechanical property in FSP zone was discussed.

The current study aims to estimate the influence of enhanced nitrogen on the hot ductility of medium carbon microalloyed steel. For this purpose, hot tensile tests were carried out at temperatures rangeing from 700°C-1000°C at a true strain rate of 0.001s^-1. The fracture surfaces and their neighboring precipitates and matrix microstructures "frozen" in tensile temperatures were observed. The dependence of hot ductility on the fracture mode and in situ microstructural changes were discussed. The results indicate that raising the nitrogen content from 0.003% to 0.014% and 0.021% was found to deteriorate the ductility as the obtained ductility trough became deeper and wider. The trough deepening caused by the addition of nitrogen was due to the formation of film-like ferrite and fine VN precipitation along the austenite grain boundaries promoting low ductility intergranular failure. On the other hand, the retarded dynamic recrystallization, the promoted deformation induced ferrite formation and precipitation at higher temperatures by enhanced nitrogen were regarded as the possible reasons for a wider trough. In summary, the above results indicate the hot ductility of medium carbon microalloyed steels is weakened to some extent by enhanced nitrogen and their windows suitable for continuous casting should be schemed very carefully.

The precipitation behavior of Z-phase was investigated during long-term aging at 650°C in an ultra low carbon 9Cr ferritic/martensitic heat resistant steel. The steel was prepared by vacuum induction melting followed by hot forging and rolling into a plate. The plate was normalized at 1100°C for 1h, cooled in air and tempered at 700°C for 1h. Bimodal nano-sized MX precipitates distribute densely and homogeneously in the matrix within martensitic lath after normalizing-and-tempering heat treatment. After aging at 650°C for 1200h, the Z-phase was found to nucleate on the larger nano-sized MX. The Z-phase and MX have the following orientation relationship: <112>_Z-phase//<001>_MX and .

In this paper, the effect of Co and Ni in AerMet100 steel on the structure stability for Fe₃C was investigated using first-principles calculations based on generalized gradient approximation (GGA) density function theory. The internal positions of atoms within the unit cell were optimized and the ground state properties such as lattice parameter, the formation energy and density of states for Fe₃C structure without and with Co or Ni((Fe, M)₃C, M=Fe, Co, Ni) were calculated. The calculated results show that the equilibrium structural parameters of Fe₃C agree with the experimental ones. The formation energy of Fe₃C is negative, while that of Fe₃C with Co or Ni are positive. The Fe₃C with the substitution of Co or Ni for Fe at the 4c sites are metastable or unstable at ambient conditions. The effect of Co and Ni on the structural stability for Fe₃C is discussed in terms of their electronic structure and chemical bonding.

Investigated in this study are precipitate evolution with and without addition of W, Co, and B in two kinds of 9-12% Cr steels (named as A and B) used for power plants after various aging time and temperature using OM, SEM, TEM, etc. Three kinds of precipitates (Cr-rich M₂₃C₆, Nb-rich and V-rich MX, W-rich and Mo-rich Laves phase) were observed and investigated in the two alloys. Upon aging, the area fraction of M₂₃C₆ increased whereas that of Laves phases decreased despite of increase in size. The area fraction of W-rich Laves phase was much higher than that of Mo-rich Laves phase, indicating that W addition, compared to that of Mo addition, is more powerful in the formation of Laves phase precipitation (specimen A). The martensitic microstructure of specimen B was more stable than that of specimen A due to the addition of cobalt and boron. The tensile test and impact test were measured and studied in relation to the long term aging effect.

By introducing ZrO₂ (4Y) powder into the thermit, Al₂O₃/ZrO₂ (4Y) composite ceramics of different composition and microstructures were prepared through combustion synthesis under high gravity, and the correlations of composition, microstructures and mechanical properties of composite ceramics were investigated. The results of XRD, SEM and EDS showed that Al₂O₃/33%ZrO₂ (4Y) were composed of random-orientated rod-shaped colonies consisting of a triangular dispersion of orderly submicron-nanometer t-ZrO₂ fibers, surrounded by inter-colony regions consisting of spherically-shaped micronmeter t-ZrO₂ grains; meanwhile, Al₂O₃/45%ZrO₂ (4Y) were comprised of spherically-shaped micron-meter t-ZrO₂ grains. Similar to the international directionally solidified Al₂O₃/ZrO₂ (Y₂O₃), the EDS results also indicated that there are no impurities, amorphous phases and grain boundaries but clean phase interfaces in two ceramic composites. Compared to the international directionally solidified Al₂O₃/ZrO₂ (Y₂O₃), the increase in hardness and flexural strength of Al₂O₃/33%ZrO₂ (4Y) in the experiment was due to small-size defect and high fracture toughness induced by compressive residual stress effect and transformation toughening mechanisms; meanwhile, high flexural strength of Al₂O₃/45%ZrO₂ (4Y) was considered to be a result of the fine spherically-shaped t-ZrO₂ grains separated from the melt under high gravity, and high fracture toughness induced by transformation toughening and micro-crack toughening mechanisms.

Epitaxial growth of non-polar thin films (a-plane ZnO) on sapphire (r-plane sapphire) were successfully implemented through metal organic chemical vapor deposition (MOCVD) and radio-frequency sputtering, respectively. For ZnO film deposited by sputtering, the growth temperature and the flow ratios of argon to oxygen were shown to significantly influence the crystalline quality and surface morphology of ZnO films. Flat surface ZnO epitaxial film can be grown by MOCVD. The epitaxial relationship between ZnO and sapphire substrate is and . The full width at half maximum (FWHM) of X-ray rocking curve for reflection peak depends on the orientation of X-ray beam toward sample surface. SEM and AFM observations show the surface morphologies of ZnO epilayers exhibit a stripe-like pattern along ZnO [0001] direction. The higher growth rate along ZnO [0001] and in-plane anisotropic lattice mismatch between a-plane ZnO and r-plane sapphire might result in the formation of such stripes.

The thermal shock behavior of hot-pressed ZrB₂-SiC composite containing 15vol.% graphite flake (ZrB₂-SiC-G) was investigated. The thermal shock testing was carried out by means of quenching into water from high temperatures (ΔT in the range of 200-1000°C). The damage introduced by the thermal shock was characterized by the degradation of bending strength. The residual strength exhibited a complex evolution and could be divided into three zones according to the variation of the temperature difference: (i) no damage zone (200-300°C), (ii) strength degradation zone (300-400°C), and (iii) low stable strength zone (400-1000°C). The minimum residual strength of 160 MPa, higher than 40% of the initial strength of 396 MPa, was obtained in the third zone of temperature difference. The surface feature of ZrB₂-SiC-G composite after the thermal shock tests was also investigated.

The oxidation process of calcium hexaboride (CaB₆) ceramic sintered body with 28wt% nickel as a sintering aid was investigated systematically in this paper. DTA-TG was used to analyze the oxidation behavior at various temperatures. The morphologies of the oxidation surfaces and the interface between the oxide layer and the bulk material were given by EPMA and BSE, respectively. Element distribution on cross-sections was measured by an energy spectrum analyzer. It is found that CaB₆-28wt%Ni shows an excellent oxidation resistance below 1173K owing to the protection provided by calcium borate on the surface. Catastrophic fast oxidation begins at 1273K. The grain boundaries act as the diffusion channels for O₂ penetration. The existence of Ni doesn't affect the oxidation behavior of the matrix CaB₆. The mechanism of oxidation was also discussed in this paper.

The effects of BN/Ti molar ratio on the self-propagating high-temperature synthesis (SHS) reaction behaviors and final products in the Ti-BN system were experimentally investigated. With an increase in the BN/Ti ratio, the combustion temperature and wave velocity first increase and then decrease with the maximum values displaying at BN/Ti=0.67. A substoichiometric TiN_1-x was obtained for BN/Ti<0.67, and a stoichiometric one was produced for BN/Ti=0.67. Moreover, the microstructure photographs of the products reveal that with the increase of the BN/Ti ratio, the grains of the ceramic phases tend to be finer.

In this paper, the microwave dielectric properties of Ca_(1-x)Zn_xLa₄Ti₅O₁₇ ceramics have been studied. The diffraction peaks of Ca_(1-x)Zn_xLa₄Ti₅O₁₇ ceramics shift to higher angles as x increases from 0 to 0.01 and nearly unchanged with x increasing from 0.01 to 0.03. A maximum density of dielectric constant value of 57 and a quality factor (Q × f) of 15000 GHz can be obtained for Ca_0.99Zn_0.01La₄Ti₅O₁₇ ceramic sintered at 1450°C for 4h. A near-zero temperature coefficient of resonant frequency (τf) of -8.1 ppm/°C can be obtained for Ca_0.99Zn_0.01La₄Ti₅O₁₇ ceramic sintered at 1450°C for 4h.

In this paper a failed Hadfield (high manganese austenite) steel crossing used in railway system was studied. The microstructure in the worn surfaces of the crossing was investigated using optical microscopy, scanning electron microscopy, transmission electron microscopy and Mössbauer spectroscopy. The results indicated that a nanocrystallization layer formed on the surface of the crossing served. The formation mechanism of the nanocrystalline is the discontinuous dynamic recrystallization. The energy for the recrystallization nucleus formation originates from the interactions between the twins, the dislocations, as well as twin and dislocation. High-density vacancies promoted the recrystallization process including the dislocation climb and the atom diffusion.

Artificial neural network (ANN) back-propagation model was developed to predict the behavior of fracture toughness and tensile strength as a function of microstructure. Both fracture toughness and tensile strength were found to increase with the increase in martensite content in a dual phase microstructure of microalloy steel. The primary objective of the ANN Back-propagation (BP) prediction model was to validate and extend the application of microalloy steels for various engineering applications. The ANN training model has been used to predict the optimum toughness properties in terms of intercritical annealing temperature and martensite content. This can be used as a practical tool for predicting the fracture toughness in other series of steels comprising dual-phase microstructures and also to optimize strength and ductility properties. The ANN model exhibited excellent comparison with the experimental results. It is concluded that predicted fracture toughness by the trained neural network model seem more reasonable compared to approximate methods. It is possible to claim that, ANN is fairly promising prediction technique if properly used. Training ANN model was introduced at first. And then the neural network architecture is designed. The performance of system is summarized at last. In order to facilitate the comparisons of predicted values, the error evaluation and mean relative error are obtained. The result show that the training model has good performance, and the experimental data and predicted data from ANN are in good coherence.

Effect of deformation induced transformation (DIT) process on ferrite grain size and ferrite transformation volume fraction in the refractory low alloy steel 12Cr1MoV by controlled rolling and controlled cooling technology were experimentally studied. Simulation experiments of hot deformation were carried out with the Gleeble-1500 system. Single-pass and multi-pass hot rolling process with different deformation temperature, deformation reduction, strain rate and cooling rate were performed separately. The ferrite grain size decreased and the ferrite volume fraction increased with decreasing deformation temperature, and the extra-fine ferrite grain about 1.01µm was obtained when the deformation temperature reached 780°C. Higher deformation reduction resulted finer ferrite grain size and higher ferrite volume fraction. Both the ferrite grain size and ferrite volume fraction decreased with increasing strain rate. The ferrite grain size decreased but the ferrite volume fraction didn't change much when the cooling rate increased. The grain size and the ferrite volume fraction were improved more by three-passes than two-passes rolling. The mechanism of grain refinement by DIT was discussed.

The straightness of the 100-meter rail after straightening is directly affected by the bending deformation during cooling before straightening, and the analysis of the temperature field in the cooling process is the basis of studying the bending deformation. By analyzing the heat boundary conditions in the cooling process, the temperature field was calculated and its variable law was analyzed by using the 3-D transient non-liner finite element method. The factors such as the solid-state phase change and the physical parameters with change of the temperature were considered, and the numerical results were coincident with the experimental data. The results show that the velocities of temperature changing at different positions of the rail's cross-section are different in the cooling progress, and the phase change and the irregular cross-section of rail are important influencing factors.

The objective of this work was to study the influence of titanium variations on the API 5L-X70 steel weld metal properties. The relationship between microstructure and toughness of the weld deposit was studied by means of full metallographic, longitudinal tensile and Charpy-V notch tests on the specimens cut transversely to the weld beads. The best combination of microstructure and impact properties was obtained in the range of 0.02-0.05% titanium. By further increasing of titanium content, the microstructure was changed from a mixture of acicular ferrite, grain-boundary ferrite, Widmanstätten ferrite to a mixture of acicular ferrite, grain-boundary ferrite, bainite and ferrite with M/A microconstituent. Therefore, the mode of fracture also changed from dimpled ductile to quasi-cleavage. Titanium-base inclusions improve impact toughness by increasing the formation of acicular ferrite in the microstructure. The amount of manganese in inclusions was decreased with addition of titanium to the weld metal.

Shear banding characterization of Zr_64.13Cu_15.75Ni_10.12Al₁₀ and Zr₆₅Cu₁₅Ni₁₀Al₁₀ bulk metallic glasses (BMGs) with significant difference in inherent plasticity and quite similar chemical composition was studied by depth sensitive macroindentaion tests with conical indenter. Well-developed shear band pattern can be found for both BMGs after indentation. Distinct difference in the shear band spacing, scale of plastic deformation region and the shear band branching in the two BMGs account for the different plasticity.

TEM investigations on crystallization behavior of a Fe₆₈C_10.5Si_4.4B_6.5P_8.6Al₂ bulk metallic glass reveals that the nano-scale fcc Fe phase formed by primary crystallization is homogeneously embedded in the amorphous matrix after heat treatment at 783 K for 30 min. With increasing heat treatment time (783 K for 45 min), a tetragonal Fe₃(C,B,P) phase encapsulates the primary fcc Fe phase suppressing the growth of the fcc Fe phase. The Fe₃(C,B,P) phase decomposes into a mixture of orthorhombic Fe₃(C,P) and tetragonal Fe₃(B,P) upon further annealing treatment at 783K.

Recent work has shown that many metallic glass properties correlate with the Poisson ratio of the glass. We have developed a new model for simulating the atomistic behavior of liquids and glasses that allows us to change the Poisson ratio, while keeping the crystalline phase cohesive energy, lattice constant, and bulk modulus fixed. A number of liquid and glass properties are shown to be directly affected by the Poisson ratio. An increasing Poisson ratio stabilizes the liquid structure relative to the crystal phase, as indicated by a significantly lower melting temperature and by a lower enthalpy of the liquid phase. The liquids clearly exhibit two changes in behavior: one at low temperatures, associated with the conventional glass transition T_g, and a second, higher temperature change associated with the shear properties of the liquids. This second crossover has a characteristic, measurable change in the liquid structure.

Bulk metallic glasses (BMGs) in pseudo-ternary (La-Ce)-Al-Cu system with high glass-forming ability (GFA) were synthesized based on the beneficial effect of the coexistence of similar elements La and Ce with similar atomic size and various valence electronic structures on GFA. With the coexistence of La and Ce in (La_xCe_1-x)₆₅Al₁₀Cu₂₅ system, bulk metallic glasses with diameters up to 12 mm can be produced by copper mold casting. Besides the high GFA, the (La_xCe_1-x)₆₅Al₁₀Cu₂₅ BMGs with x = 0.6 and 0.7 exhibit low glass transition temperature T_g around 362 K and wide supercooled liquid regions ΔT_x (ΔT_x = T_x - T_g, where T_x is the onset temperature of crystallization) of about 80 K. Compared with ternary La-Al-Cu and Ce-Al-Cu systems, significant improvement of GFA for the (La-Ce)-Al-Cu system is caused by the coexistence of similar elements La and Ce, and the mechanism is discussed from a thermodynamic viewpoint.

This paper reports on some physical properties of a conducting polymer, polypyrrole, coated textiles. Polypyrrole was coated on textiles chemically through in-situ solution or vapor polymerisation to produce conducting textiles. The effects of the conductive coating on the physical and mechanical properties of the fibrous materials are presented. The coating durability and conductivity of the textiles have also been examined.

As novel smart materials, shape memory polymer (SMP) and its composite (SMPC) have the ability to regain its original shape after undergoing significant deformation upon heating or other external stimuli such as light, chemic condition and so on. Their special behaviors much depends on the glass transitions due to the increasing of material temperature. Dynamic Mechanical Analysis (DMA) tests are performed on the styrene-based SMP and its carbon fiber fabric reinforced SMPC to investigate their glass transition behaviors. Three glass transition critical temperatures of SMP or SMPC are defined and a method to determine their values from DMA tests is supposed. A glass transition model is developed to describe the glass transition behaviors of SMP or SMPC based on the results of DMA tests. Numerical calculations illustrate the method determining the glass transition critical temperature is reasonable and the model can well predict the glass transition behaviors of SMP or SMPC.

A high entropy alloy of composition CoCrCuFeNiAl_0.5 is mainly composed of a face centered cubic (FCC) solid solution phase. The tensile and compressive properties of the alloy were investigated; the alloy exhibited a tensile strength of 707 MPa, together with a large plastic strain limit of 19%.

Ti₄₀Cu₄₀Ni₁₀Zr_10-xSc_x (x = 0.5 and 1, at%) alloys were prepared by copper mould casting method. Microstructures of the ɸ 3 mm rod alloys were investigated by XRD and SEM. The results showed that the ɸ 3 mm rods were glassy matrix with TiCu crystalline phase. Mechanical properties were studied by compressive test. Ti₄₀Cu₄₀Ni₁₀Zr₉Sc₁ alloy exhibited good compressive strength over 2200 MPa and superior compressive deformation is about 7.9%.

The giant magnetoimpedance (GMI) effect in Co75Fe4.2Si8B12Nb0.8 melt extraction wires annealed in a vacuum furnace at 450°C holding for 10min, 20min, 25min, 30min and 40min, respectively, is investigated. Strong GMI effect is observed at a typical frequency of 37MHz. The observation on the GMI effect indicates that the anisotropy field dominated by the anneal treatment is vital to the GMI ratio △Z/Z(%) and its field sensitivity. The improvement on GMI effect when anneal time is less than 20min is ascribed to the stress release, decreased anisotropy field and increased permeability. The decrease of GMI effect when anneal time is over 25min results from nanocrystalline phase grow up inducing the crystalline anisotropy field increase. Suitable annealed wires possess large GMI ratio (855%) and little anisotropy field achieving high field sensitivity to 151%/Oe. These results indicate these Co-based melt extraction wires are excellent for using in novel field sensors applications.

In this study, the cracking behavior in the bulk and the stress-strain responses of partially crystallized Zr-Ti-Cu-Ni-Be bulk metallic glass after surface modification were investigated. The compressive plasticity was found to be dependent on the surface conditions. The plasticity was enhanced significantly by a complete removal of visible surface flaws. The electro-plating of copper on the rough surface also increased the plasticity of Zr base BMG of the present study. The beneficial effect of the electro-plating can be attributed to filling and smoothening effect due to plating and/or the ductilization of the surface, both of which does not favor crack nucleation. We also found the cracking behavior in the bulk different from the surface region. The cracks in the center of the sample were not straight, but wavy, suggesting the cracks were deflected by or attracted to crystalline particles. A high magnification view of a crack revealed small triangular shaped crystals along the crack path.

The crystallization of melt-spun Fe-Pt-B amorphous alloy with a thickness of 20 µm in steady high magnetic field (HMF) was investigated. The intensity of the applied magnetic field is 0-10 T along with the ribbons annealed at temperature ranging from 673 K to 873 K. The direction of the performed magnetic field is perpendicular to the direction of surface velocity of the Cu wheel. The thermal magnetic properties of the samples were obtained by the thermal gravity analyzer with a magnet attached to the outside of the furnace filled with flowing inert gas. The phase transformations of Fe-Pt-B amorphous alloy on heating with and without the steady HMF were studied by X-ray diffractometry together with the melt-spun ribbon. The average grain size of the samples annealed in HMF was about 10 nm calculated from the XRD patterns. The HMF was thought to be effective on the refinement of nanograins which were produced by the crystallization of the amorphous ribbon during the annealing process.

Fe-based amorphous alloys are widely used in the magnetic apparatus and generally produced by the single-roller copper-wheel melt spinning method. Spray forming is one of the rapid solidification techniques as the spinning method is, seldom used to fabricate Fe-based amorphous alloys. However in this paper, a Fe-based alloy with the nominal composition of Fe_73.5Cu₁Nb₃Si_13.5B₉ (at.%) alloy was fabricated by spray forming technique with the aim of investigating the formation of amorphous phases and novel microstructures by the high cooling rate involved in this process. The gas/metal mass flow rate used was 0.15, and nitrogen was used as the atomization gas. The resulting deposit and the overspray powder had a median diameter of about 50 μm with a total weight of about 2.2 kg. The microstructure of the deposit was observed by utilizing the X-Ray Diffraction (XRD) and Optical Microscope (OM), as well as Transmission Electron Microscope (TEM), which revealed a heterogeneous varying with the thickness, presenting at center region 15 mm and at border 8 mm with porosities 4 and 9%, respectively. The thicker region showed a fully crystalline microstructure with grain size of about 250nm, whereas the thinner region had a partially amorphous phase with an average grain size of 40nm. The overspray powder was fully crystallized with the grain size of 80nm which was calculated from XRD spectra using the Scherrer formula. The magnetic properties were measured through VSM, giving a poor magnetic saturation value of about 0.3~0.6T. The coercive force was increased significantly.

Cold gas dynamic spraying (CGDS) technique makes use of high-speed gas current to spray diversified metal, alloy and composite materials under room temperature or with a little heated. It is one kind of novel surface engineering technologies, aimed at eliminating such negative influences as oxidation, gasification, melt, crystallization and gas decomposition and so on existing in hot spraying technologies. Due to its peculiar characteristics such as low spraying temperature, non-oxidation, low stress among coating layers, compactification, and high utilization rate of raw materials, as well as effective applications in the domain of fabricating coatings, the CGDS technique has attracted great attention. As it has the advantages aforementioned, especially avoiding the changes of material properties resulted from high spraying temperature, CGDS provides a kind of revolutionary means for fabricating such heat-sensitive materials as amorphous alloys. The paper reviews the current situation and application development of the CGDS technique, and presents our preliminary exploration of fabricating bulk Fe-based amorphous alloy via CGDS together with mechanical milling process.

A new kind of composite with a bi-continuous structure was produced by pressure infiltrating melt Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 into porous SiC which was made by powder metallurgy. Microstructure investigations of the composite show that the melt alloy was fully infiltrated into the voids of porous SiC and quenched into amorphous state. Both the amorphous alloy and the porous SiC exhibit a three-dimensional interconnected net structure. The study of thermal properties reveals that the addition of porous SiC reduces the width of supercooled liquid region of the composite. The bi-continuous composite presents 2% plastic strain and ultimate strength of 1250MPa.

Two-dimensional photonic crystals (2D-PCs) with Ge₂Sb₂Te₅ (GST) nanohole arrays were prepared by the nanosphere lithography (NSL) process. A primary factor of PCs is that the refractive index (n) and the n-modulation can be realized by using the GST films, which exhibit a reversible phase transformation between amorphous and crystalline states by laser illumination. The polystyrene (PS) spheres with a diameter of 500 nm were spin-coated on Si substrate and subsequently reduced by O₂-plasma treatment. The reduced spheres were utilized as a lift-off mask of the NSL process and their size and separation could be precisely controlled. Amorphous GST films were thermally evaporated and then the reduced PS spheres were removed. The fabricated GST nanohole arrays were observed by SEM and AFM. The nanohole diameters are nearly linearly reduced with increasing plasma-treatment time (t). The reduction rate (δ) for the conditions of this work was evaluated to be ~ 0.92 nm/s. The period (Λ) and filling factor (η) of PCs are structure parameters that determine their photonic bandgaps (PBGs). η-modulation can be easily achieved via a control of t and the Λ can be also modulated by the use of PS spheres with specific diameter. In addition, the PBGs for the fabricated GST 2D PC were calculated by considering the amorphous and crystalline states of GST.

Metal-alumina joints have found various practical applications in electronic devices and high technology industry. However, making of sound metal ceramic brazed couple is still a challenge in terms of its direct application in the industry. In this work we successfully braze copper with Al₂O₃ ceramic using Zr_52.5Cu_17.9Ni_14.6Al₁₀Ti₅ bulk metallic glass forming alloy as filler alloy. The shear strength of the joints can reach 140 MPa, and the microstructrural analysis confirms a reliable chemical boning of the interface. The results show that the bulk metallic glass forming alloys with high concentration of active elements are prospective for using as filler alloy in metal-ceramic bonding.

The micro-porous polymer electrolytes membranes(PEMs), notably electro-spun fiber mats, have been suggested to give an improved ionic conductivity. However, the mat-type PEMs have a poor mechanical and dimensional stability because of their inevitable porous nature. In this study, we suggest a new PEM system based on poly(vinylidene fluoride)(PVdF) mats, which can overwhelm such shortcomings of the porous mats by introducing another component, poly(4-vinyl pyridine)(P4VP), into the mats. The tensile strength of PVdF/P4VP membrane was considerably improved compared with that of pristine PVdF membrane under dry and wet conditions. The ionic conductivity was also improved by about 10 times than that of PVdF mat. A micro- to nano-size gap was formed at the interfaces between PVdF nanofiber and P4VP, and this may act as a channel for fast ion transportation under wet condition.

Ti-based bulk metallic glasses (BMGs), Ti₄₀Zr₂₅Cu₉Ni₈Be₁₈, were prepared by phase transition cooling (PTC) and copper mould casting(CMC) technology. Ti₄₀Zr₂₅Cu₉Ni₈Be₁₈ glassy rod of more than 13 mm in diameter was prepared by PTC technology which shows the high cooling rate obtained by this technology. No obviously differences in thermal property were found between the BMGs prepared by the PTC and CMC technology. The compressive plasticity of the alloy was apparently changed, from 8% using CMC to 37% by using PTC technology. PTC technology is probably a promising method for preparing BMG and an effective way to increase the plasticity of BMGs.

Ni₄₂Cu₅Ti₂₀Zr_21.5Al₈Si_3.5 bulk metallic glasses rods with diameters of 1 mm and 3 mm, were prepared by arc melting of composing elements in a Ti-gettered argon atmosphere. The compressive deformation and fracture behavior of the amorphous alloy samples with different size were investigated by testing machine and scanning electron microscope. The compressive stress-strain curves of 1 mm and 3 mm samples exhibited 4.5% and 0% plastic strain, while the compressive fracture strength for 1 mm and 3 mm rod is 4691 MPa and 2631 MPa, respectively. The compressive fracture surface of different size sample consisted of shear zone and non-shear one. Typical vein patterns with some melting drops can be seen on the shear region of 1 mm rod, while fish-bone shape patterns can be observed on 3 mm specimen surface. Some interesting different spacing periodic ripples existed on the non-shear zone of 1 and 3 mm rods. On the side surface of 1 mm sample, high density of shear bands was observed. The skip of shear bands can be seen on 1 mm sample surface. The mechanisms of the effect of sample size on fracture strength and plasticity of the Ni-based amorphous alloy are discussed.

The mechanical property of a new bulk metallic glass Zr_50.7Cu₂₈Ni₉Al_12.3, which owns 5% room-temperature plasticity, is investigated at low temperatures 193K and 123K. It is indicated that the yield strength and the plasticity significantly increase by 12.8% and 50% respectively as testing temperature is lowered from 298K (at room temperature) to 123K (in liquid nitrogen). The dense and multiple shear bands which contribute to the improved ductility are observed on the side surface of these samples fractured at low-temperature. Detailed study of the stress-strain curves for the samples deformed at low temperature show that more serrations and smaller stress drop form due to generation of more much shear bands.

In order to define the relation between yield behavior and yield criterion of bulk metallic glass (BMG), analysis and investigations have been carried out for interrelations between yield strengths and the angle which fracture plane deviates from the 45° plane of the maximum shear stress in tensile and compressive test of BMG. Tensile fracture angle is consistent with the result calculated by theory of disconnected slip line field and Mises yield condition. Compressive fracture angle is consistent with the result calculated by Coulomb yield condition. Conclusion: BMG obeys different yield criterions in different stress states. For tensile, it follows Mises criterion, and for compression, it follows Coulomb criterion.

As an important class of natural and engineered materials, periodic microstructural composites have drawn substantial attention from the material research community for their excellent flexibility in tailoring various desirable physical behaviors. To develop periodic cellular composites for multifunctional applications, this paper presents a unified design framework for combining stiffness and a range of physical properties governed by quasi-harmonic partial differential equations. A multiphase microstructural configuration is sought within a periodic base-cell design domain using topology optimization. To deal with conflicting properties, e.g. conductivity/permeability versus bulk modulus, the optimum is sought in a Pareto sense. Illustrative examples demonstrate the capability of the presented procedure for the design of multiphysical composites and tissue scaffolds.

The main influence factors on mechanical properties of ceramic composites reinforced by spherical nano-micro particles are investigated in this study. The sizes of the particles vary from micro (0.5 µm) to nano-scale (40 nm). Two kinds of representative volume elements (RVE) are applied to describe different arrays of nano-micro particles. One is the nesting array in which a nano-particle is nested within the microscopic particles, and the other is the enwrapping array in which a micro-particle is enwrapped by some nano-particles. The finite element (FE) analysis is conducted by the global-local homogenization method with precise period boundary conditions. The numerical simulation is performed with the changes of radius ratios of nano-micro particles, volume fractions and the interfacial properties. The results show that the effective Young's modulus of the composites with the enwrapping array has an obvious increase as compared to those with the nesting array for high volume fraction of micro-particles, and it is dependent on the radius ratios of nano-micro particles within certain volume fractions. The interfacial damage between nano-micro particles and their matrix decreases significantly the effective Young's modulus. It is significant to improve the mechanical properties of ceramic materials by mixing some nano- and micro-particles into the matrix with mature interface properties.

In this paper, the nanocrystalling composite Mg-Ni-TiO₂-CNTs was made by mechanical ball milling under hydrogen pressure of 5.0×10^-5Pa, The hydrogen storage properties and operation temperatures were investigated. It was found that the composite can absorb 7.5wt.% hydrogen in 60s under 5.0×10^-5Pa hydrogen pressure and desorb 6.5wt% hydrogen in 600s at 260°C under 5.0×10^-5Pa hydrogen pressure. The composite has very high absorption, hydrogen capacity and remarkable kinetic properties in hydriding /dehydeiding process. TiO₂, Ni and CNTs were used as additive to improve the hydrogen storage performance. They can be utilized as an effective catalyst to improve hydriding/dehydriding performance of hydrogen storage material and lead to pronounced enhancement on the hydrogen storage property of Mg. The results showed that the composite has potential application in the future.

As a kind of novel biopolymer material with good biodegradability and biocompatibility, poly(β-hydroxybutyrate-co-valerate)(PHBV) was introduced into organic/inorganic network structure of nanocomposite hydrogels prepared by in-situ free-radical polymerization based on monomer N-isopropylacrylamide(NIPAM) and physical cross-linker hectorite. As viewed from appearance of the hydrogels, obvious change occurred from transparent to white with the increase of PHBV content, which reflects the structural shift from homogeneity to inhomogeneity. The swelling ratio and swelling kinetics of thermo-sensitive poly(NIPAM/PHBV/Hectorite) hydrogels with different PHBV content was investigated by gravimetric method. It was found that the incorporation of PHBV decreases the swelling ratio of pure poly(NIPAM/Hectorite) hydrogels on account of hydrophobicity of PHBV. Furthermore, in the case of swelling kinetics, the result of linear regression shows that relaxation of polymer chains of the hydrogels controls the swelling process.

Electroless Ni-plated short carbon fiber reinforced geopolymer matrix composites with various carbon fiber/matrix interface coating thicknesses have been successfully fabricated. The influences of coating thickness on the mechanical properties and fracture behavior have been investigated by three-point bending test and scanning electron microscopy. The flexural strength and Young's modulus of Ni-plated short carbon fiber reinforced geopolymer composites exhibit maximums as the average fiber coating thickness increases, but the work of fracture has a sharp decrease, and the fracture manner changes from ductile to brittle. This is mainly attributed to the fact that the carbon fibers favor breakage rather than pulling-out during loading because of the higher interface bonding strength of fiber/matrix, and pliability of the carbon fibers decreases with the increase of the coating thickness.

Hypereutectic Al-Si alloys with fine and evenly distributed Si precipitates have superior mechanical properties In this study, hypereutectic Al-Si alloy powders which contained 15 and 20wt% Si were prepared by a gas atomization process. 1, 3 and 5wt% AlN particles were blended with the Al-Si alloy powders using turbular mixer. The mixture was consolidated by Hot Press at 550°C for 1h under 60MPa. Relative density of the sintered samples was about 98% of theoretical density. This study was investigated by two ways. One is the effect of reinforcement weight fraction and the other is the effect of Silicon contents on the mechanical properties of the composite. Microstructural characterization and phase evaluation were carried out using X-ray Diffraction, Scanning Electron Microscopy equipped with Energy Dispersive Spectrometer. The results showed that the smaller the reinforcement particle size was and the better its distribution was, the higher ultimate tensile strength and hardness were.

Al₂O₃-20vol%Fe₇₀Co₃₀ composite powders have been prepared by high energy ball milling a mixture of Al₂O₃ powder and Fe₇₀Co₃₀ alloy powder. The Fe₇₀Co₃₀ alloy powder was also prepared by mechanical alloying of Fe and Co powders using the same process. The effects of milling duration from 8 to 48 hours on microstructure and magnetic properties of the nanostructured composite powders have been studied by means of X-ray Diffractometry (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). It was found that the nanostructured composite powder particles with irregular shapes and Fe₇₀Co₃₀ alloy particles being embedded in them formed after 8 hours of milling. The average grain size of the Al₂O₃ matrix reduced drastically to less than 18nm after 16 hours of milling. On the other hand, the embedded alloy particles demonstrated almost unchanged average grain size in the range of 14-15nm. Magnetic properties of the powder compacts at room temperature were measured from hysteresis curves, and show strong dependence of the milling time, with the coercivity increasing from 67.1 up to 127.9kOe with increasing the milling time from 8 to 48 hours. The possible microstructural reasons for this dependence are discussed.

TiC/Ti6A14V composites with different Zr additions were prepared successfully in a consumable vacuum arc furnace equipped with a water-cooled copper crucible and the effect of the Zr content on the microstructure and mechanical property of 15 vol.%TiC/Ti6A14V composites was investigated by XRD, SEM and hardness testing. The results show that when the level of Zr addition is less than 4 wt.%, the morphology of the primary TiC in the composites is dendrite, and the petal-shape, piece-shape or palpus-shape eutectic TiC separates out around the primary TiC. The average size of the primary TiC decreases and the amount of eutectic TiC increases gradually with increasing Zr content. The effects of Zr on morphology of the primary TiC weaken with further addition of Zr. And the hardness (HRC) of composites was obviously increased in the whole range of Zr addition. The refinement mechanism of Zr was attributed to the combined effects of increase in nucleation rate at the constitutionally supercooled zone ahead of the solidification front and reduction in growth rate.

Polyethylene (PE) film was coated with nanosilica-polyamide layer using rod Mayer process. The nanosilica-polyamide system was prepared by dispersing nanosilica (nano-SiO₂) powder into solvent borne polyamide binder under vigorous stirring. Various compositions of nanosilica-polyamide slurry were prepared. The thickness of the layer was about four µm and eight µm for single and double layer coating respectively. A battery of characterization procedures were used to study the properties of the nanocomposite coating. The uniformity of silica dispersion was probed using elemental mapping procedure and scanning electron microscopy (SEM). With the introduction of nanosilica to polyamide binder, the visible light transmittance and ultra-violet (UV) radiation of nanosilica-polyamide system reduced with increasing nanosilica content and coating layer thickness. Infrared (IR) effectiveness (between 7 µm to 13 µm wavelengths) measurements by FTIR also showed that nanosilica-polyamide system coating on PE film surface greatly improved the thermic effect of PE film. The nanocomposite coating containing 14 wt% nanosilica and with eight µm coating thickness has improved the IR effectiveness of PE to 76%. Thermic effect of the nanocomposite increased with increasing nanosilica content and coating thickness.

Multiwalled carbon nanotubes (MWCNTs) grafted with poly(L-lactide-e-caprolactone) (PCLA) were synthesized by in situ ring opening polymerization and used as a reinforcement for neat PCLA. The analyzed data revealed that the applied tensile load on the composite was transferred to the functionalized MWCNTs, leading to a strain failure of the MWCNTs rather than an adhesive failure between the MWCNTs and the matrix. In comparison between the functionalized and pristine MWCNTs, as reinforcement materials for PCLA random copolymers (80% L-lactide (LA), 20% e-caprolactone (CL)) (PCLAR80), the functionalized MWCNTs are more effective reinforcement materials than pristine MWCNTs. In comparison with the neat PCLAR80, the increasing in tensile strength (28.03%) and elongation at failure (49.6%) when functionalized MWCNT loading reaches 1.0 wt%, indicate that an effective reinforcement of the MWCNT-OH-g-PCLA.

The use of thermal spray coatings provides protection to the surfaces operating in severe environments. The main goal of the current work is to investigate the possibility of using a high velocity air fuel (HVAF) thermally sprayed wear resistant Ti(Al,O)/Al₂O₃ coating on tool steel (H13) which is used for making dies for aluminium high pressure die casting and dummy blocks aluminium extrusion.

A feedstock of Ti(Al,O)/Al₂O₃ composite powder was produced from a mixture of Al and TiO₂ powders by high energy mechanical milling, followed by a thermal reaction process. The feedstock was then thermally sprayed using a high velocity air-fuel (HVAF) technique onto H13 steel substrates to produce a composite coating.

The present study describes and compares the tribological properties such as friction and sliding wear rate of the coating both at room and high temperature (700°C). The wear resistance of the coating was investigated by a tribometer using a spherical ended alumina pin as a counter body under dry and lubricating conditions. The results showed that composite coating has lower wear rate at high temperature than at room temperature without using lubricant. The composite coating was characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD). This paper reports the experimental observations and discusses the wear resistance performance of the coatings at room and high temperatures.

Al₂O₃ particles reinforced ZL109 composite was prepared by in situ reaction between Fe₂O₃ and Al. The phases were identified by XRD and the microstructures were observed by SEM and TEM. The Al₂O₃ particles in sub-micron size distribute uniformly in the matrix and Fe displaced from the in situ reaction forms net-like alloy phases with Cu, Ni, Al, Mn ect. The hardness and the tensile strength at room temperature of the composites have a small increase compared with the matrix. However, the tensile strength at 350°C can reach 92.18 MPa, which is 18.87 MPa higher than that of the matrix. The mechanism of the reaction in the Fe₂O₃/Al system was studied by DSC. The reaction between Fe₂O₃ and Al involves two steps. The first step in which Fe₂O₃ reacts with Al to form FeO and Al₂O₃ takes place at the matrix alloy melting temperature. The second step in which FeO reacts with Al to form Fe and Al₂O₃ takes place at a higher temperature.

This article studies about the mechanical strength of different functionalized Carbon nanotubes (CNTs) reinforced Polyethylene (PE) fiber composite fabricated by melt spinning. There are four types of CNTs used, which are called as produced, carboxylated, octadecylated, polymer wrapped CNTs. Influence of mechanical drawing (melt spinning) on the mechanical strength of fibers is measured by direct comparison with mechanical strength of bulk type functionalized CNTs polymer composites, which fabricated using hot press. Dispersion and interfacial bonding strength/adhesion of CNTs with PE matrix are investigated through fracture surfaces image analysis. Functionalized CNTs composites show a significant improvement of mechanical strength of pure polymer than non functionalized CNTs polymer composite. Whereas polymer wrapped CNTs polymer composite give the highest mechanical strength in this study. Mechanical strength of bulk composites are significantly increased after mechanical drawing process indicates that melts spinning may influence on the crystallization of polymer. Fracture surface analysis revealed that additional functionalized CNTs enhanced dispersion and interfacial bonding with polymer matrix.

Spark plasma sintering (SPS) is employed to fabricate self-lubricating Al₂O₃-SrSO₄ nanocomposites incorporated with and without Ag addition. The friction and wear properties have been evaluated using a high temperature friction and wear tester from room temperature to 600°C in dry sliding against alumina ball. X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analyzer were used to investigate microstructure and self-lubrication mechanisms of nanocomposites after wear tests at different temperatures. Al₂O₃-SrSO₄ nanocomposites with optimum compositional combinations exhibit low and stable friction coefficients of 0.22 and wear rates in the order of 10^-5 mm³/Nm at high temperatures. At low temperature, the Ag additives in the composite form a discontinuous lubricating film to effectively reduce friction and wear. With increasing test temperature, plastic deformation of SrSO₄ during sliding plays an important role in formation of lubricating films on worn surfaces to reduce the friction and wear.

The hot deformation behavior of in situ TiB₂ reinforced 6351 Al composites synthesized by mixed salt reaction method was investigated by compression tests in the temperature range of 300-550°C and strain rate range of 0.001-10 s^-1. The microstructure evolution during compression was observed by employing transmission electron microscopy (TEM). The results show that, the flow stress decreases with decreasing strain rate and increasing temperature, and the activation energy is about 169.98 kJ/mol. Microstructure observation indicates that the complex dislocation structures were formed around the TiB₂ particulate at the lower temperature and the lower strain rate and their density is reducing with increasing temperature. Dynamic recovery and recrystalized structures were observed in the lower and higher deformation temperature, respectively. At the higher strain rate, the interface separation between TiB₂ particulate and Al matrix alloy and TiB₂ particulate cracking were found in this study. The main restoration mechanisms of TiB₂/6351 composites during hot deformation are dynamic recovery and dynamic recrystallization.

A metal matrix composite coating reinforced by ZrC-ZrB₂ particulates has been successfully fabricated utilizing the in situ reaction of Zr, B₄C and Fe pre-placed mixed powders by gas tungsten arc welding (GTAW) cladding process. Various volume fraction of ZrC-ZrB₂ particulates composite coatings were produced through cladding different weight ratios of Zr+B₄C (30%, 50%, 70%) to improve the wear resistance of AISI1020 steel substrate. The Microstructure of the coating was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive spectrum (EDS), meantime microhardness and wear resistance at room temperature of the composite coating were examined by means of Microhardness Tester and Wear Tester, respectively. The results show that the main phases of the composite coating obtained by GTAW are ZrC, ZrB₂ and α-Fe, ZrC exhibits hexahedron and petal shapes, ZrC-ZrB₂ compound presents acicular and clubbed forms. With the increase of content of Zr+B₄C, the maximum volume fraction of ZrC-ZrB₂ particulates can reach 16.5%, microhardness is up to 1300HV, and wear resistance is about twenty times higher than that of AISI1020 steel substrate.

(TiBw+TiCp)/Ti6Al4V composites were fabricated by reactive hot-pressing at the temperature range of 800~1200°C using the starting materials of TiB₂, C and Ti6Al4V powders. The XRD results suggested that the reaction between C and Ti happened 900°C and above, while the reaction between TiB₂ and Ti happen at 1100°C and above. SEM results also suggested that the reaction between C and Ti was prior to that between TiB₂ and Ti. With the increase of the sintering temperature, the size of TiC particle and TiB whisker reinforcements increased gradually. The TiC particle was formed at the boundaries of original Ti6Al4V particles, while the TiB whiskers grew toward the inside of Ti6Al4V particles, which resulted in a strong bonding between neighboring Ti6Al4V particles. The results of hardness and relative density tests showed that the (TiBw+TiCp)/Ti6Al4V composites sintered at 1100°C had the highest hardness and relative density compared with that sintered at other temperatures.

In this work, a series of ZrO₂/ZrW₂O₈ ceramic composites with different amounts of ZrW₂O₈ were successfully prepared by calcining the precursors synthesized using co-precipitation route at 1150°C for 3 h. The X-ray diffraction (XRD) data confirmed that the composites only consisted of α-ZrW₂O₈ phase and m-ZrO₂ phase. The scanning electron microscopy (SEM) analysis of the synthesized ZrO₂/ZrW₂O₈ composites showed that the specimens had good mixed-uniformities. In addition, the thermal expansion coefficients of the composites decreased with increased amounts of negative thermal expansion ZrW₂O₈, specimen with 26wt% ZrW₂O₈ shows almost zero thermal expansion and its average thermal expansion coefficient is -0.5897×10^-6K^-1 in the temperature range from 30°C to 600°C.

The microplastic deformation behavior of 20 vol.% SiCp/Al composites with various SiC particle sizes were investigated. The SiC particles are in four nominal sizes of 1, 5, 20 and 56 µm. The experimental results showed that the micro-yield strength is very sensitive to composite microstructure features. As the particle size increases, the micro-yield strength of composites decrease firstly, and then increase. The observed results were attributed to thermal residual stress and dislocation density due to the large difference in coefficient of thermal expansion between the matrix and reinforcement.

The fracture process and the structure changes of the multi-walled carbon nanotubes (MCNT) during the mechanical ball milling process were investigated and the samples of ball milled powder were observed by SEM. The results indicate that the MCNT turned into nano-whiskers or nano-particles during the ball milling process. The pre-milled MCNT could be distributed in Cu powders homogeneously. The bulk MCNT/Cu nanocomposite were fabricated by hot pressing the mixed MCNT/Cu powders at a temperature of 1073 K under a pressure of 20 MPa and the microstructure of the composites were investigated. It has been found that the multi-walled carbon nanotubes distributed in copper evenly.

Mg-3Ni-2MnO2 hydrogen storage nanocomposites added with different composition (1%~4%) carbon nanotubes (CNTs) were prepared by mechanical milling under the atmosphere of hydrogen. Different mechanical milling process parameter has been discussed in this paper. Study on hydrogen storage ability of Mg-3Ni-2MnO2-nCNTs with different composition carbon nanotubes has been carried out. The result show that Mg-3Ni-2MnO2-nCNTs excellent heat conductivity and good hydrogen storage (more than 6%vol) ability, the CNTs improve the mass transfer and heat transfer properties of the Mg-3Ni-2MnO2, thus enhancing the kinetic property of hydrogen absorption and desorption of the hydrogen storage nanocomposites, and raising the hydrogen storage capacity. Due to the addition of the carbon nanotubes, the milling stress in the process of preparing the Mg-based namocomposites is reduced, the components can be closely bonded easily, and the additives can play better catalytic roles enhancing the kinetic property of hydrogen absorption and desorption of the hydrogen storage nanocomposites, and raising the hydrogen storage capacity. Due to the addition of the carbon nanotubes, the milling stress in the process of preparing the Mg-based namocomposites is reduced, the components can be closely bonded easily, and the additives can play better catalytic roles.

A dense and uniform Si_p/LG5 composite were fabricated by squeeze casting technology, and high temperature diffusion treatment was adapted to the composite. Microstructure observation indicated that Si transformed from irregular particles to 3D-structure. Fine dispersive precipitates Si were also observed on Si-Al interface and within Al matrix, smoothing and improving the interface. Based on the microstructure observation, three transformation stages were designated: melting, dissolution and precipitation, solidification. Thermodynamics and kinetics of the transformation can be explained by Gibbs-Thomson effect.

Intermetallic matrix composites reinforced with ceramic particles have received a great deal of attention. Iron aluminide is known to be a good material for the matrix in such composites. Two processes were used to fabricate FeAl-TiB₂ intermetallic matrix composites. One was liquid melt in-situ mixing, and the other was arc melting and suction casting processes. FeAl-TiB₂ IMCs obtained by two different methods were investigated to elucidate the influence of TiB₂ content. In both methods, the grain size in the FeAl alloy decreased with the presence of titanium diboride. The grain size of in-situFeAl-TiB₂ IMCs became smaller than that of arc FeAl-TiB₂ IMCs. Significant increase in fracture stress and hardness was achieved in the composites. The in-situ process gives clean, contamination-free matrix/reinforcement interface which maintained good bonding causing high load bearing capability. This contributed to the increase in the mechanical properties of composites.

In this study, three types of functionally graded Al₁₈B₄O₃₃/Mg composites which consisted of 2, 3 and 4 layers and where volume fractions of Al₁₈B₄O₃₃ were gradually changing from 0 to 35% were fabricated using squeeze infiltration technique. The mechanical parameters of each layer were measured for the analysis of residual stress. Elastic finite element numerical models were applied to the analysis of thermal residual stress. The analytic results showed that the residual stresses were significantly decreased in the macrointerface with increasing the number of layer.

Hypereutectic Al-Si alloys are one of the most interesting material for high strength structural components because they have low coefficient of thermal expansion (CTE) as well as high wear resistance and mechanical properties. However, Al-based alloys have lower hardness and wear resistance than ferrous alloys and these disadvantages restrict the use of al-based alloy. They could be overcome by making composite reinforced with ceramic particles. TiC was good candidate for the reinforcement of the alloy. Al-20wt%Si was fabricated by gas atomization and 1, 3 and 5wt%TiC were mixed to these powders by turbular mixer for 10h with 45rpm. The mixture was hot-pressed at 550℃C for 1h under 60MPa pressure. Relative density of the sintered samples was about 98% of theoretical density. The effect of reinforcements on mechanical properties and wear resistance of composite was investgated. Strength, hardness and wear resistance of the sintered sample were improved by the grain refinement and dispersion strengthening.

The corrosion behavior of the silicon carbide particulates (17.5 vol.%) reinforced 5A06 aluminum alloy metal matrix composite (MMC) and the 5A06 aluminum matrix alloy has been studied in 3.5% NaCl solution at 35°C by using electrochemical impedance spectroscopy (EIS). Analysis of the results, which were obtained from optical (OM) and scanning electron microscopy (SEM) attached with energy dispersion spectroscopy (EDS), indicate that the corrosion behavior of the materials studied was mainly localized corrosion due to the presence of intermetallics (Al(Mn, Fe), Al(Si, Mg)) on the surface and crevices at the interface of SiCp/matrix. More numerous, wider spread, smaller and shallower pits were noted on the composite surface relative to the unreinforced matrix alloy during immersion. However, the pitting morphology on both materials was completely different from crystallographic type of pitting. Crystallographic pitting occurred by anodically polarizing the materials above the pitting potential. Further, the occurrence of an inductive time constant at lower frequencies region and the lower impedance as compared to that of the matrix alloy indicate that the corrosion extent of the composite was more severe than that of the matrix alloy, both materials were immersed for varied periods. Two different equivalent circuits were proposed and applied to analyze the EIS measurements, which can simulate the impedance of the composite and the matrix alloy under corrosive environment.

Composites based on multi-walled carbon nanotubes (MWCNTs)s and poly(L-lactide) (PLLA) were prepared by using solvent casting method. Both carboxylated MWCNTs and pristine MWCNTs were considered in order to investigate the interactions between PLLA and MWCNTs and to understand the role of the filler in the biodegradability. In vitro degradation studies were performed by measurement of weight loss, FT-IR, DSC and SEM over a 30 weeks period. Pristine MWCNTs and carboxylated MWCNTs had a different effect on the degradation of PLLA. Thermal properties of MWCNTs based PLLA composites changed compared to neat PLLA. A possible mechanism of MWCNTs effect on the degradation of PLLA was discussed.

Aluminum borate whisker (9(Al₂O₃)·(B₂O₃)) reinforced AS52(with and without strontium modification) metal matrix composites (MMC) were fabricated by the squeeze infiltration method. Creep rupture test was carried out at 150°C and 100 MPa condition. Results showed that Alborex reinforcement and modified polygonal shape Mg₂Si phase contributed to the enhancement of mechanical properties and creep resistance. Creep rupture time was increased 11% and minimum creep rate was decreased 17% in the composite. At the Alborex/matrix interface, uniform thin layer of MgO was formed. The initiation of micro-voids at the reinforcement/matrix or Mg₂Si/matrix interface was followed by their growth and coalescence to macro-cracks.

A phase mixture based finite element model was developed and the deformation of nanocrystalline nickel was studied in this paper. Monocrystalline grain interior phase and amorphous grain boundary phase were applied in the finite element model respectively. The digital topological model, which followed the Log-normal distribution, was generated by a systematic method. The experimental strain and strain rate hardening behaviors and severe nonlinearity phenomena of nanocrystalline nickel can be predicted very well by the numerical simulation. By presenting evolution process of Mises stress and equivalent plastic strain, we found shear localization phenomenon and much faster plastic deformation in grain boundary phase. These result in the relatively lower ductility of nanocrystalline nickel compared with that of coarse-grain counterparts.

It is well-known that TiO₂ nanoparticles are highly efficient photocatalysts in decomposing organic substance in wastewater, especially when they are used in suspension state. However, if TiO₂ nanoparticles cannot be withdrawn and reused, it is difficult to apply them in purification of wastewater due to the economic consideration. In present work, TiO₂/SiO₂/Fe₃O₄ core-shell magnetic nanoparticles, constituted by Fe₃O₄ core, SiO₂ intermediary layer and the TiO₂ out-shell, have been prepared and applied in photocatalytic degradation of a modulated methylene blue containing water. The results indicate that the as-prepared TiO₂/SiO₂/Fe₃O₄ nanoparticles possess high photocatalytic activity and the methylene blue in wastewater can be degraded quickly. Through comparing with the photocatalytic performance of the famous commercial P25 TiO₂ nanoparticles in the same reaction condition, it has been found that as-prepared TiO₂/SiO₂/Fe₃O₄ nanoparticles exhibit similar photocatalytic activity to commercial P25 TiO₂ nanoparticles in the photocatalytic degradation of methylene blue containing water. But the TiO₂/SiO₂/Fe₃O₄ nanoparticles used in suspension state can be simply recovered from the liquid by using a magnet or a magnetic field. So the cost of wastewater purification by photocatalytic degradation with TiO₂/SiO₂/Fe₃O₄ nanoparticles can be significantly reduced through reuse of the photocatalyst. It implies that TiO₂/SiO₂/Fe₃O₄ nanoparticles possess the potential for industrial application.

Here we used the iron oxide nanoparticles derived from ferritin as catalyst for the synthesis of carbon nanotubes (CNTs) by the chemical vapor deposition (CVD) of coal gas. It has been found that the structure and morphology of CNTs can be tailored, to some degree, by varying the experimental conditions such as catalyst loading and process parameters. In addition to straight CNTs, some Y-branched CNTs were also obtained, which might be due to the sulfur species in the coal gas.

Titanium, zirconia and HAp were known as good biocompatible materials for tissue engineering. Osteblastic cell response is influence by the surface topography of material and its chemical composition as well. To evaluate the influence of different chemical compositions on osteoblast-like cells the specimens were polished until they have almost identical surface roughness. The commercially pure titanium, zirconia/alumina composite and nano-sized hydroxyapatite (HAp) specimens synthesized by hydrothermal method were used to evaluate the cell attachment, proliferation and differentiation. Confocal laser microscopy was used measurement of surface roughness, and flourescence microscopy and SEM were used to evaluate initial cell attachment and morphology after 3 hours. MTS assay was performed for cell proliferation after 1, 3, 7 days and ALP assay was used for cell differentiation after 7, 10, 14 days of cell culture period. Surface topography of nano-HAp specimen was almost identical compared with those of titanium and zirconia specimen. Under this condition, proliferation and differentiation of MC3T3-E1 cells was not significantly different with those on titanium and zirconia specimen. However, cells on Nano-HAp specimen showed quicker and more active cellular reaction for attachment when measured by the expression of adhesion proteins through confocal laser microscopy. The results suggested that the new nano-sized HAp can be applied as a suitable material for skeletal tissue engineering.

Taking the wide band gap one-dimensional (1-D) tungsten oxide nanowires as an example, we here demonstrate systematically the physical characteristics of thermally processed nanowires at temperatures ranging from 400°C to 1000°C, for the first time. Accompanied by a significant drop of specific surface area from 151 m²/g for the as-prepared nanowires to 109 m²/g and 66 m²/g subject to annealing at 400°C and 450°C, dramatically morphology evolution and phase transformation have also been observed. The nanostructured bundles became straighter, larger in diameters and shorter in length, and eventually became irregular particles with size up to 5 µm. The Brunauer-Emmett-Tettler (BET) result suggests that 400°C can be considered as a top temperature limit in nanodevice design where high surface area is important, e.g. in gas sensors. A protocol for thermally processing of these bundled tungsten nanowires has been established.

The purpose of experiment was to produce bulk nanocrystalline Zn by mechanical attrition. The bulk nanocrystalline Zn produced by mechanical attrition was studied. The microstructural evolution during cryomilling and subsequent room temperature milling was characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In this paper, Nanocrystalline Zn was produced by insitu consolidation of Zn elemental powder using mechanical attrition at liquid nitrogen and room temperature. For the samples studied, the longest elongation of 65% and highest stress of 200 MPa is obtained in nanocrystalline Zn during tensile testing at the condition of strain rate (10^-3 sec^-1) and 20°C which is equal to 0.43 T_m (T_m is the melting temperature of pure Zn).

The reaction synthesis of barium boride (BaB6) nanoparticles under low temperature was investigated in this study. X-ray diffraction (XRD) was used to investigate the phase and the structure of BaB₆. The characterization for microstructure was performed by Field Emission Scanning Electron Microscope (FESEM) with EDS, TEM, Fourier transform infrared (FTIR) spectroscopy and Raman scattering spectroscopy. It is concluded that BaB₆ nanoparticles can be successfully prepared under low temperature at 500°C. XRD pattern shows that the nanoparticles are consisted of predominantly (110)-oriented BaB₆ phase. The powders are polygonal-like shape with the average size of 200 nanometers. TEM identified that each nanoparticle shows perfect single crystal and cubic structure. The boron-to-barium atomic ratio of 5.24:1 was determined, less than the stoichiometric ratio of 6:1. BaB₆ nanoparticles can absorb infrared spectrum at 459, 690, 993, 1329, 1619, 2449 and 3423cm^-1 in the test range of 400~4000cm^-1, respectively. Three peaks at 677.1, 823.5 and 1116.4cm^-1 can be observed clearly from the Raman spectra of BaB₆ nanoparticles at room temperature. The results showed that the electron dispersion of B₆ octahedron in BaB₆ is two-dimensional pancake-type without lattice distortion, which may account for the unique physical properties of BaB₆ nanoparticles.

Two alloy systems were designed across the β/β+α"–phase boundary. The small addition of O and Fe was found to be very effective in stabilizing the β–phase and modifying the mechanical properties. The cold rolling effect on the mechanical properties was different between the β+α" alloys and the single β–phase alloys. The presence of 20%Zr in the alloys was a reason behind the severe change of mechanical properties with β–phase stability and with cold working.

The in vitro and in vivo biocompatibility of the ZnO nanoparticles were evaluated using cell model and animal model, by MTT assay, flow cell cytometry, pathological optical and electron microscopy examinations. Both the L929 cell and Hela cell proliferative activity were strongly inhibited by the presence of ZnO nanoparticles, no matter cultured with low dose and high dose suspension. AnnexinV-FITC/PI-FCM assay showed that the number of necrotic cell and apoptotic cell increased significantly. Feeding the ZnO nanoparticle suspension through digestive tract would lead to the damage to some primary organs (heart, lung, liver and kidney). Further investigation by TEM showed the expanded sarcoplasmic reticulum and organelle vacuolation features.

Bulk nanocrystalline Fe₃Al materials were prepared by aluminothermic reaction on the substrates with different thickness of 5~15 mm. Grain size of the materials was measured by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Compressive strength and hardness of the materials were tested. The results showed the materials consisted of amorphous and nanocrystalline phases. With the substrate thickness increasing, amount of the nanocrystalline phase increased and that of the amorphous decreased and grain size of the nanocrystalline increased and a few grains in micrometer appeared in part areas of the materials. Yield strength and hardness of the materials remarkably decreased with the substrate thickness.

In order to avoid the "metallic smile" appearance of metal wires when undergoing orthodontic treatment, epoxy resin/polytetrafluorethylene coating TiNi arch wires were made by dipping method. TiO₂ and FeFe₂O₄ were chosen as dyes in order to match the color of teeth and the color schemes were fixed by spectrophotometer method. The biocompatibility of coating was also examined. The results showed that the cytotoxicity of the coating was grade I, and without mutagenesis and carcinogenesis. Skin sensitization assay showed no erythema or oedema response and epithelial was integrated according to mucous membrane irritation. Thus, good behavior in clinic can be anticipated.

The final solidification structures of Vacuum Arc Remelting (VAR) ingots depend on the temperature distribution and fluid motion within the molten pool. In this paper, a three-dimensional multi-physics macroscale model for VAR is developed, based on the modular CFD software PHYSICA. This model is used to provide estimates of process parameters and to study complex physical phenomena, such as liquid metal flow with turbulence, heat transfer, solidification, and magnetohydrodynamics in the VAR process. The macromodel is coupled to a microscale solidification model. The micromodel combines stochastic nucleation and a modified decentred square/octahedron method to describe dendritic growth with a finite difference computation of solute diffusion. The resulting multiscale model allows prediction of the formation of microstructures in the solidifying mushy zone. This gives a better understanding of the whole VAR process from operational conditions to final ingot microstructures, as well as an essential first step in defect prediction.

Plastic deformation that occurs in a heavy slab during plane-strain rolling was investigated by the finite element analysis. A cylindrical pore was assumed to be located along the transverse direction of a slab. The effective strain was found to be the largest at the sub-surface layer and the smallest at the middle layer, where the shear strain developed the least. Pore closure was most difficult at the middle layer. This is where hydrostatic stress in addition to effective strain developed the least. Rolling torques, rolling forces and pressure distributions at the roll/slab interface were investigated as well, under various conditions.

A numerical modeling of the welding arc and weld pool is studied for moving GTA welding to investigate the effect of the surface active element oxygen and the plasma drag force on the weld shape. Based on the 2D axisymmetric numerical modeling of the argon arc, the heat flux, current density and plasma drag force are obtained under different welding currents. Numerical calculations to the weld pool development are carried out for moving GTA welding on SUS304 stainless steel with different oxygen contents 30 ppm and 220 ppm, respectively. The results show that the plasma drag force is another dominating driving force affecting the liquid pool flow pattern, except for the Marangoni force. The different welding currents will change the temperature distribution and plasma drag force on the pool surface, and affect the strength of Marangoni convection and the weld shape. The weld D/W ratio initially increases, followed by a constant value around 0.5 with the increasing welding current under high oxygen content. The weld D/W ratio under the low oxygen content slightly decreases with the increasing welding current. The predicted weld shape by simulation agrees well with experimental results.

The paper based on the SOLA-VOF, depended on the meaning of the equation result in the algebra and geometry, brings forward a new idea and the rapid iterative arithmetic. According to the rapid iterative arithmetic, a program of the rapid calculating method of flow field and the numerical simulation experiment using the standard casting have been made by the author. The result showed that the calculating efficiency has increased by 3~4 times than before, the accuracy equals to the SOLA-VOF, which can meet the requirements of the application.

A two dimensional (2D) cellular automaton (CA) - lattice Boltzmann (LB) model is presented to investigate the effects of forced melt convection on the solutal dendritic growth. In the model, the CA approach of simulating the dendritic growth is incorporated with the kinetic-based lattice Boltzmann method (LBM) for numerically solving the melt flow and solute transport. Two sets of distribution functions are used in the LBM to model the convective-diffusion phenomena during dendritic growth. After validating the model by comparing the numerical results with the theoretical solutions, it is applied to simulate the single and multi dendritic growth of Al-Cu alloys without and with a forced convection. The typical asymmetric growth features of convective dendrite are reproduced and the dendritic morphology is strongly influenced by melt convection. The simulated convective multi dendritic features by the present model are also compared with that by the CA-NS model. The present model is found to be more computationally efficient and numerically stable than the CA-NS model.

Conventional finite element (FE) analysis of bulk metal forming processes often breaks down due to severe mesh distortion. In recent years, meshless methods have been considerably developed for structural applications. The main feature of these methods is that the problem domain is represented by a set of nodes, and a finite element mesh is unnecessary. This new generation of computational methods can avoid time-consuming meshing and remeshing. A meshless method based on reproducing kernel particle method (RKPM) is applied to bulk metal forming analysis. The displacement shape functions are developed from a reproducing kernel (RK) approximation that satisfies consistency conditions. The shape function is modified to impose essential boundary conditions accurately and expediently. A material kernel function that deforms with the material is introduced to assure the stability of the RKPM shape function during large deformations. A program based on RKPM is developed to simulate two examples of bulk metal forming process such as ring compression and cold upsetting, and numerical results demonstrate the performance of the meshless method in bulk metal forming analysis.

The technique of severe plastic deformation (SPD) enables one to produce metals and alloys with an ultrafine grain size of about 100 nm and less. As the mechanical properties of such ultrafine grained materials are governed by the plastic deformation during the SPD process, the understanding of the stress and strain development in a workpiece is very important for optimizing the SPD process design and for microstructural control. The objectives of this work is to present a constitutive model based on the dislocation density and dislocation cell evolution for large plastic strains as applied to equal channel angular pressing (ECAP). This paper briefly introduces the constitutive model and presents the results obtained with this model for ECAP by the finite element method.

An analytical model based on Eshelby equivalent inclusion approach and Mori-Tanaka mean field extension was established by introducing numerical matrix and composite secant/tangent moduli to simulate the stress-strain curve of particulate reinforced composite. The same modeling work was also carried out by FEM analysis based on the unit cell model using a commercial ANSYS code. The modeling results by both models on evolution of the load carried by the SiC particles during straining provide strong evidences to back up the strengthening mechanism of the load sharing. The modeling was also carried out to study the influence of different volume fractions and aspect ratios on elastic modulus and yield strength of the composites with different reinforcing particles to get a better understanding of strengthening mechanisms of the materials. A concept of microstructure design for particulate reinforced materials was argued based on new developments in understanding of the relationship between properties and microstructure. The optimal geometry of particulate reinforcement was discussed in respect to the best match up with matrix mechanical behavior.

The criterion and research technique of auto body panels stiffness are introduced in this work, and the finite element models (FEM) of cylindrical shallow shell that could represent auto body panels are established. Simulations of forming, springback and stiffness on cylindrical shallow shell are carried out. The simulations show great accuracy with the experimental results. Extensive simulated results of the influence laws of material mechanical properties on stiffness are achieved, such as yield strength, strain-hardening exponent, Young's modulus, anisotropy parameter and strength coefficient. With comparison of the weight coefficient of material mechanical properties on stiffness, it can be concluded that the Yong's modulus, strain-hardening exponent and yield strength are key influencing factors of stiffness. With the analysis of distribution of the strain after cylindrical shallow shell forming, plastic deformation during the forming process resulting in work-hardening of the material is one of the main reasons for increasing stiffness.

Bulk nanocrystalline Ni samples were prepared by plasma evaporation method combined with hot pressure sintering. The compressive mechanical properties of the bulk samples were tested under quasi-static strain rates at room temperature and the evolution of microstructure of bulk sample before and after compression was studied. The experimental results indicated that the bulk samples show a good combination of strength and ductility and have obvious strain rate sensitivity. Both dislocation glide mediated and grain boundary mediated deformation mechanism were found to be main operating deformation mechanisms for the bulk samples based on the mechanical behaviors and grain refinement after compression.

Based on theoretical analysis, finite element software ABAQUS and MSC.Fatigue were used to establish the forecasting model of fatigue life for laser shot peening (LSP) process. By using a standard stretch test sample of 6061-T6 aluminium alloy, the residual stress field induced by LSP was analyzed with ABAQUS code firstly, and then the stress field model was imported into MSC.Fatigue code for the crack growth analysis. The residual stress distribution and its effect on crack propagation life induced by LSP are numerical studied, and the fatigue life is predicted. The results show that numerical simulation approach is valuable for analyzing the fatigue crack growth and influence of process parameters on fatigue life.

In this study, the (FePt)_100-xCu_x (x=0, 4.6, 6.7, 8.8, 10.9) (FePtCu) alloy films were prepared by co-sputtering. The effects of Cu addition content and heat treatment on the nanostructure and magnetic properties of the polycrystalline (FePt)_100-xCu_x films are reported. The experimental results show that the ordering temperature of the (FePt)_100-xCu_x (x=6.7) films reduced to 320°C, which is much lower than that of the FePt alloy. After heat treatment at 600°C for 1 hour, the (FePt)_100-xCu_x (x=6.7) film shows a coercive force of 15 kOe and the magnetization of 576 emu/cc. The magnetic properties of the FePtCu films can be adjusted by varying the Cu content in the films. The enhancement of the magnetic properties of the FePtCu films mainly resulted from the formation of the order L1₀ phase. DSC traces of as-deposited disorder films at different heating rates, to evaluate the crystallization of the order phase, showed that the addition of Cu atoms reduced the activation energy of ordering from 217 kJ/mol to 87 kJ/mol for the (FePt)_100-xCu_x films (x= 0 and 6.7, respectively). The reduction of the ordering temperature and corresponding activation energy might due to the solid solution of the Cu atoms in the FePt films.

In this work, top-configuration exchange-biasing NiFe(y)/IrMn(90Å) systems have been investigated with three different conditions: (a) the substrate temperature (T_s) was kept at room temperature (RT) only, (b) T_s at RT with an in-plane field (h) = 500 Oe deposition during deposition, and (c) T_s = RT with h during deposition and postdeposition annealing in the field at T_A = 250°C for 1h, with the samples field cooled to RT. High resolution electron cross-sectional transmission electron microscopy (HR X-TEM) and x-ray results reveal that the IrMn (111) texturing plays a key role in the exchange-biasing field (H_ex) and interfacial energy (J_k). The H_ex versus y result shows that H_ex increases when y decreases. Since J_k = H_exM_sy, where M_s is NiFe magnetization, it is easy to derive H_ex = J_k/(M_sy). Therefore, if H_ex is inversely proportional to y, with J_k/M_s constant, we find H_exy = constant. In short, the y dependence of J_k is similar to that of M_s for each curve. The H_c is inversely proportional to y because of the surface pinning effects from the Ta/NiFe and NiFe/IrMn interfaces. Finally, the optimal values for H_ex and J_k are 220 Oe and 0.075 erg/cm², respectively.

The effects of Hf substitution and C content on the magnetic properties, phase evolution, and microstructure of melt spun (Sm, Pr)Co_7-xHf_xC_y (x = 0-0.5; y = 0-0.14) ribbons have been studied. A proper Hf substitution is helpful not only in stabilizing 1:7 phase but also in enhancing its magnetic anisotropy field. As a result, magnetic properties of B_r = 6.4 kG, _iH_c = 7.3 kOe and (BH)_max = 8.7 MGOe for SmCo_6.9Hf_0.1 ribbons are obtained. Besides, a small amount of C addition in the ribbons could slightly modify phase constitution and effectively refine their microstructure to strengthen the exchange coupling effect between magnetic grains. Furthermore, a slight Pr substitution for Sm may further increase the magnetization and the magnetic properties of the ribbons. The optimal magnetic properties of B_r = 7.1 kG, _iH_c = 8.5kOe and (BH)_max = 11.2 MGOe could be achieved for the directly quenched Sm_0.8Pr_0.2Co_6.9Hf_0.1C_0.12 ribbons.

We designed the one-dimensional photonic quasi-crystals (1D PQCs) arrays for application to the flat-band (FB) pass filters using a transfer matrix method (TMM). In this work, the PQCs of the combinations of SiO₂-TiO₂ and SiO₂-ITO were designed with the centre wavelength of 1.550 µm at an incident angle of 8°. The width of flat-transmission bands increases with increasing the number of cavity. For a SiO₂/TiO₂–based PQC with 3-cavity structure, the FB-width was evaluated to be about 0.7 nm and the insertion loss was approximately 0.3 dB. In addition, the band-center wavelength exhibited a blue shift with an increase of incident angle and their band widths are uniform for specific θ_i-ranges. An application of this FB-pass filter to a wavelength division multiplexing (WDM) device was also proposed. We believe that the PQC-based devices could be comprehensively applied to the new conceptional optical passive and active devices.

CVD diamond coating was deposited on to 13%wt. Co-containing tungsten cemented carbide surfaces using a hot filament chemical vapor deposition (HFCVD) to improve wear properties and performance of WC-13%wt.Co. Prior to the deposition of the diamond films, a W-C gradient intermediate layer had been sputtered on WC-13%wt.Co. The surface and cross-section morphology, phase transformation, and grain size distribution of the samples were investigated by means of field emission scanning electron microscope (SEM), X-ray diffractometer (XRD), and atomic force microscope (AFM), respectively. The results show that W-C gradient intermediate layers can effectively reduce the diffusion of Co in cemented carbide substrates during diamond deposition process, resulting high nucleation density and ultra smooth nanocrystalline diamond films.

The Nano-TiO₂/Diatomite compound photocatalyst is used to degrade rhodamine B dye wastewater in photochemical reactor. The test result indicates that the rate of photodegradation of rhodamine B is influenced by reactive conditions. The best technical conditions are concentration of rhodamine B solution 10mg/L, ultraviolet light 300W, the compound photocatalyst amount used 1g/L, the pH 5.8, reaction time 20min. Under these conditions the rate of photodegradation of rhodamine B may reach as high as 97.80%. And the efficiency of photodegradation of catalyst only has a little changed in recycling.

This work deals with modeling of 1-3 thermoelectroelastic composites with a doubly periodic array of piezoelectric fibers under arbitrary combination of mechanical, electrical loads and a uniform temperature field. The finite element method (FEM) based on a unit cell model is extended to take into account the thermoelectroelastic effect. The FE predictions of effective properties for several typical periodic microstructures are presented, and their influences on effective properties are discussed. A comparison with the Mori-Tanaka method is made to estimate the application scope of micromechanics. The study is useful for the design and assessment of composites.

The calculations of mechanic and electronic properties for MgAl₂O₄ spinel under pressure are presented by first principle. The lattice constants and internal parameters are in good agreement with the available experimental results. The calculations for bulk modulus, elastic constants, energy gaps, bond lengths for the nearest neighbor cation-O anion and their pressure dependence show an increase of bulk modulus, elastic constants, energy gaps in high symmetry and a decrease of cation-O anion bond lengths. A transition from indirect gap material to direct one is found due to applying pressure. Up to 70GPa, there is no sign of structural instability.

The electronic and optical properties of MgV_0.125Al_1.875O₄ are investigated by use of the first principle. The calculated results indicate that the V-doped compound is semiconductor with a small gap 0.2102eV. It is concluded that the doping element V has specific rule in the MgAl2O4 spinel, which leads it showing finite value DOS at the Fermi level and makes the total DOS gaps smaller than that of MgAl₂O₄. In MgV_0.125Al_1.875O₄, the influencing factor on the optical process is that the 3d orbitals of V ion are highly localized and the part of 3d bands well incorporate into the conduction band, which very benefit to charge transfer transitions between O2p orbitals to the hybridized V3d orbitals near the conduction band. The absorption intensifies in the visible zone due to the V doping. The charge-transfer transitions around 282nm and 433nm between V and O are attributed to the optical excitation and deexcitation process, respectively, in agreement with experimental observations.

The service life of industrial components is limited predominantly by Chemical corrosion/mechanical wear. The project is concerned with the investigation of the capability of Ti(Al,O)/Al₂O₃ coatings to improve the service life of tool steel (H13) used for dies in aluminium high pressure die casting.

This paper gives a general review on the research work conducted at the University of Waikato on producing and evaluating the titanium/alumina based composite coatings. The powder feedstocks for making the composite coatings were produced by high energy mechanical milling of a mixture of Al and TiO₂ powders in two different molar ratios followed by a thermal reaction process. The feedstocks were then thermally sprayed using a high velocity air-fuel (HVAF) technique on H13 steel substrates to produce a Ti(Al,O)/Al₂O₃ composite coatings. The performance of the coating was assessed in terms of thermal shock resistance and reaction kinetics with molten aluminium. The composite powders and coatings were characterized using scanning electron microscopy (SEM), optical microscopy and X-ray diffractometry (XRD).

High current pulsed electron beam (HCPEB) has been developing as a useful tool for surface modification of materials. This paper presents our research work on surface modification of metallic materials, such as mold steel, stainless steel and magnesium alloy, with a HCPEB equipment of working parameters as electron energy 27keV, pulse duration ~1µs and energy density ~5J/cm². Investigations performed have shown that the most pronounced changes of phase-structure state and properties occurring in the near-surface layer. The formation mechanism of surface craters and their evolution regularity are discussed based on the elucidation of non-equilibrium temperature filed and different kinds of stress formed during pulsed electron beam treatment. After the HCPEB treatments, samples show significant improvements in measurements of wear and corrosion resistance.