Advanced Materials and Processing 2010

The following sections are included:

• PREFACE

• CONTENTS

Extensive numerical simulation and experimental measurements have been conducted to understand the piezoresistivity characteristics and the working mechanisms of highly sensitive strain sensors made from carbon nanotubes (CNTs) embedded polymer nanocomposites. When using two kinds of multi-walled carbon nanotubes (MWNTs), it was identified that the piezoresistivity characteristics of two sensors are different. When using comparatively straight MWNTs of a large diameter, named as MWNT-7, the fundamental working mechanism of this sensor is the tunneling resistance change among CNTs due to the distance change caused by applied strains. However, for another type of MWNTs, which is of a very small diameter and seriously curved shapes, and named as LMWNT-10, the main working mechanism of the sensor may be the piezoresistivity of MWNTs themselves due to deformation of MWNTs. Furthermore, for the sensors made from MWNT-7/epoxy, further numerical and experimental investigations have been carried out to explore the effects of processing parameters and material properties on sensor sensitivity. Both numerical and experimental results indicate that a higher tunneling resistance or higher ratio of the tunneling resistance to the total resistance of the sensor leads to a higher sensor sensitivity. Processing conditions and material properties play a role in determining the sensor sensitivity.

The microstructure evolution of the localized shear band in a cold-rolled commercial titanium was systematically investigated by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). A shear band with a width of approximately 25 μm was formed in the cold-rolled titanium and the microstructure inside the shear band was mainly nanograins with average size of 70 nm after 83% cold rolling reduction. TEM observations revealed that the grain refinement inside shear band was completely via a shear deformation-induced splitting and breaking-down of twin lamellae process.

In this study, Mg-Zr-Ca alloys were developed for new biodegradable bone implant materials. The microstructure and mechanical property of the Mg-xZr-yCa (x = 0.5, 1.0 and y = 1.0, 2.0 %, wt.% hereafter) alloys were characterized by optical microscopy, compressive and hardness tests. The in vitro cytotoxicity of the alloys was assessed using osteoblast-like SaOS2 cells. The corrosion behavior of these alloys was evaluated by soaking the alloys in simulated body fluid (SBF) and modified minimum essential medium (MMEM). Results indicated that the mechanical properties of the Mg-Zr-Ca are in the range of the mechanical properties of natural bone. The corrosion rate and biocompatibility decrease with the increase of the Ca content in the Mg-Zr-Ca alloys. The solutions of SBF and MMEM with the immersion of the Mg-Zr-Ca alloys show strong alkalization. The Zr addition to the Mg-Zr-Ca alloys leads to an increase in the corrosion resistance, compressive strength and the ductility of the alloys, and a decrease in the elastic modulus of the Mg-Zr-Ca alloys.

Hydroxyapatite (HAp) was synthesized using a hydrothermal treatment method. Nanosized calcium carbonate (CaCO₃) was used as the calcium source, while (NH₄)₂HPO₄ was used as the phosphorous source. Well-crystallized HAp and a small amount of β-tricalcium phosphate (β-TCP) were obtained after the hydrothermal reaction. FT-IR spectra show that under conditions of pH 6 and 250°C, the functional groups of OH^- and PO₄^3- were stronger than those under pH 10. This exhibits that the powder synthesized at pH 6 has more HAp phase than that at pH 10. SEM and TEM images show that HAp exhibits a rod-like shape about 10μm long and about 0.7μm wide at pH 6 and 250°C. After hydrothermal reaction at pH 6 and 250°C, most products are rod-like HAp with a small amount of β-TCP synthesized as a byproduct and some residual CaCO₃.

The magnetization process of the micro-wire arrays with glass covered amorphous wires (GCAWs) and NiFe/Cu composite wires (CWs) has been modeled with three hysteresis loops. In a multi-core orthogonal fluxgate sensor the micro-wire array sensing element presents a complicated magnetization process due to the operation mode that the excitation field is in the circumferential direction and the sensing field is in the axial direction. Fitting with this application, micro-wire arrays present large orthogonal fluxgate responses resulting from their anisotropy and domain structures. GCAWs have a circumferential anisotropy with a small angle to axial direction due to the core-shell domain structure. CWs present helical anisotropy with easy axis inclined to the circular direction. Correspondingly, the axial loop has been modeled with small coercivity and small susceptibility, and the circular loop has been modeled with large coercivity and large susceptibility. The axial-circular loop is based on the measured gating curves and has been simplified to linear dependence of the axial magnetization on the circular field. Based on the experimental measurement results and hypothesized models of the micro-wire arrays, an analytical model for the 2nd harmonic sensitivity of multi-core orthogonal fluxgate sensors has been established. Expressions of the 2nd harmonic output and the sensitivity derived by Fourier analysis show that the number of wires, anisotropy field, initial susceptibility and frequency are the key parameters determining the sensitivity.

Silicon oxide (SiO_x) nanowires have many applications due to their electrical, mechanical and optical properties. Many methods have been reported for the synthesis of SiO_x nanowires. In this paper, previously, we made Ni/SiO₂/Si substrates by dry oxidation and nickel sputtering. Then we successfully fabricated SiO_x nanowires on Ni/SiO₂/Si substrates with hydrogen gas by using simple heating process. We figured out the best temperature and best time duration for SiO_x nanowires' fabrication on Ni/SiO₂/Si substrate. Field emission scanning electron microscope (FE-SEM), field emission transmission electron microscope (FE-TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were taken to analyze these nanowires.

We have deposited TiO_xN_y thin films on Si(100) substrates at 500 °C using RF PECVD system. Titanium iso-propoxide was used as precursor with different nitrogen flow rate to control oxygen and nitrogen contents in the films. Changes of chemical states of constituent elements in the deposited films were examined by XPS analysis. The data showed that with increasing nitrogen flow rate, the total amounts of nitrogen and titanium were increased while that of oxygen was decreased, resulting in a binding energy shift toward high energy side. The characteristics of film growth orientation and structure as well as morphology change behavior were also analyzed by XRD, TED, FT-IR, TEM, and SEM. Deposition at higher nitrogen flow rate results in finer clusters with a nanograin size and more effective photocatalytic TiO_xN_y thin films with hydrophilic surface.

We report photoluminescence in the self-ion implanted silicon wafers annealed from room temperature to 950°C. The annealing temperature has been demonstrated to be a key factor which induces the dominant photoluminescence structures changed from broadband, W line, S bands, R line, to D bands with its increase. The optimal annealed temperature ranges for these features are obtained. At the low annealing temperatures (≤ 650°C), the PL spectra were predominated by several sharp peaks which originate from point defects at low record temperatures and by broadband which originate from cluster defects at high record temperature. At higher annealing temperature (> 650°C), the PL spectra were only dominated by D₁ band which undergoes red-shift and widening with increasing record temperature.

Lithium niobate hollow spheres and octahedra with rough surface have been successfully fabricated from a novel H₂(H₂O)Nb₂O₆ precursor by in situ combustion treatment. X-ray diffraction and scanning electronic microscopy were used to study the phase composition and microstructure of the obtained lithium niobate. Experimental results demonstrated that H₂(H₂O)Nb₂O₆ hollow spheres and octahedra can be facilely transformed into hexagonal phase LiNbO₃ crystallites without destroying the microstructures, even though through an intense combustion treatment. These hollow and rough octahedral structures may open up large perspectives for LiNbO₃. The present in situ conversion strategy by coating flexible H₂(H₂O)Nb₂O₆ precursors to form microscopic reactors, could also be extended to other niobates with various structures.

To extend the practical applications of the bulk metallic glasses (BMGs), the preparation of the metallic glass coatings on various substrates becomes an important research issue. Among the interfacial properties of the coatings, the adhesion between films and substrates is the most crucial. In this study, amorphous Zr₆₁Al_7.5Ni₁₀Cu_17.5Si₄ (ZrAlNiCuSi) thin films were deposited on SUS304 stainless steel at various sputtering powers by DC sputtering. According to the scratch tests, the introduction of the Cr and Ti buffer layers effectively improves the adhesion between the amorphous thin films and substrate without changing the surface properties, such as roughness and morphology. The antimicrobial results show that the biological activities of these microbes, except Acinetobacter baumannii, are effectively suppressed during the test period.

In this article, ZnO nanorod arrays were successfully prepared on the indium-doped tin oxide (ITO) by electrochemical deposition process in solution of 0.0015M Zn nitrate (Zn (NO₃)₂·6H₂O) and 0.028M methenamine (C₆H₁₂N₄). Morphology of ZnO nanorods were affected by growth condition such as to control current density. The fabricated ZnO nanorods were characterized by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). And the photovoltaic properties of the ZnO nanorods were evaluated using 1.5 solar simulator.

In the paper, NbTiAlVTaLa_x (molar ratio, x=0, 0.1, 0.2) high entropy alloys were prepared by arc melting mixtures of the pure metal elements. The NbTiAlVTaLa_x alloys are composed mainly of BCC solid solution, and have a typical cast dendritic microstructure. The cryogenic resistivities of NbTiAlVTaLa_x, CoCrFeNiCu and CoCrFeNiAl high entropy alloys had been investigated. With the increase of La addition, the resistivities of NbTiAlVTaLa_x alloys increase. With the temperature increasing, the resistivity of CoCrFeNiCu alloy decreases, while that of CoCrFeNiAl alloy increases.

Based on the steady flow in a tube, a mathematical model has been established for the consideration of centrifuging force field by combining the equations of continuity, conservation of momentum and general energy. Effects of centrifugal field on the filling and solidification are modeled by two accessional terms: centrifugal force and Chorios force. In addition, the transfer of heat by convection is considered to achieve a coupling calculation of velocity field and temperature field. The solution of pressure item is avoided by introducing the stream function ψ(x,y) and the eddy function ξ(x,y). Corresponding difference formats for the simultaneous equations of centrifugal filling, the accessional terms and the solidifying latent heat have been established by the finite difference technique. Furthermore, the centrifugal filling and solidification processes in a horizontal tube are summarized to interpret the mechanism by which internal defects are formed in centrifugal castings.

TiO₂ nanotube arrays were fabricated by anodic oxidation method at different applied voltages and electrochemical properties of the TiO₂ nanotube arrays were investigated. At higher applied voltage, the average pore size and the length of the tubes were increased due to an increase in the rate of TiO₂ formation and dissolution during the anodic oxidation. TiO₂ nanotube electrode fabricated at applied voltage of 30V delivered the 1st discharge capacity of about 235μAh/cm². Although the electrode showed a large irreversible capacity during the initial charge/discharge process, it exhibited excellent cycle performance until the 40th cycle because the larger pore size allowed homogeneous contact between the tubes and liquid electrolyte by easy penetration of liquid electrolyte into the tubes.

This study examined the microstructure and high temperature tensile properties of Mg-5Sn-3Al-1Zn-xCe (x=0, 0.5 and 1.0 wt.%) alloys. The alloys were melted in a steel crucible under a CO₂+SF₆ atmosphere and poured into a preheated permanent mold at 200°C. The microstructure of the Mg-5Sn-3Al-1Zn alloy consisted mainly of α-Mg, Mg₁₇Al₁₂ and Mg₂Sn phases. With increasing Ce content, an Al₁₁Ce₃ phase was newly formed on the grain boundaries. The results showed the tensile strength at room temperature decreased with increasing Ce content but increased at elevated temperatures.

Sonication is powerful agitation. Deposited films and electrochemical kinetics parameters were affected. The effects of micro-jet on the deposition rate and shock wave pressure on the smooth of deposited film had been studied. The bath was 0.095 mol/dm³ NiSO₄6H₂O, 0.005 mol/dm³ Na₂MoO₄, 0.3 mol/dm³ NaH₂PO₂, 0.06 mol/dm³ Na₃C₆H₅O₇2H₂O, and pH 8.5. The temperature was 353 ± 3 K. The plating rate in sonication had a little faster compared with that in stationary state with micro-jet effects. The thickness of plated film was affected with bath temperature and bath composite. When the concentration ratio of Ni and Mo increased and ratio of Mo was decreased, thickness was thicker. The plated film was an amorphous. Plating rate was faster with micro-jet. The surface was smoothed with shock wave pressures.

Naked Co_68.25Fe_4.5Si_12.25B₁₅ amorphous wires of 67μm, 56μm, 52μm, 47μm and 31μm in diameter are produced by melt extraction method. Their giant magneto impedance (GMI) effect is investigated at frequencies from 0.1MHz to13MHz. Significant diameter dependence of GMI effect is studied. Thicker wires exhibit strong GMI effect and have clear characteristic frequencies at which their impedance ratio ΔZ/Z are largest. Largest impedance response is obtained in 67μm wires with the ΔZ/Z of 442% and field sensitivity of 71.5%/Oe. Wires of 31μm in diameter show increasing ΔZ/Z as frequency and have a steady field sensitivity of 30.7-33.6%/Oe in a wide frequency range from 3MHz to 13MHz. The different frequency dependence of GMI effect is discussed in the light of the skin effect. These amorphous wires are suitable for applications in high performance field sensors and can fit different demand.

In the present study, the effect of ytterbium (Yb) addition on the microstructure and tensile properties of Mg-5Al alloys was investigated. Experimental results showed that the microstructure of the Mg-5Al alloy consisted mainly of α-Mg and Mg₁₇Al₁₂ phases. In addition, an Al₂Yb phase was newly formed on the grain boundaries and its volume percent was increased with increasing Yb content. The tensile strength, yield strength and elongation were decreased at ambient temperature with increasing Yb content. At elevated temperature, however, the tensile strength and yield strength were significantly improved while the elongation was decreased.

This paper reports on the finite element analysis of the warm deep-drawing process of 1vol% CNTs/AZ91D composite sheet. We prepare the simulation with two primary aims, first to have firsthand knowledge of warm deep-drawing process of the composite sheet, second to investigate the dependence of the drawing performance of 1vol% CNTs/AZ91D composite on forming temperature and blank holder force (BHF). Based on this simulation, we study deep-drawing performance of the CNTs/AZ91D composite under different forming temperature and different blank holder force conditions. We found that the composite sheet possess poor drawing performance below the forming temperature of 100 °C. With the increase of temperature, the deep drawing performance improved, and the drawing performance up to the top at 250 °C. In addition, the blank holder force (BHF) of the warm deep-drawing process should be selected from 5 kN to 8 kN for the composite sheet, which has a thickness of 1 mm and diameter of 160 mm.

Shot peening is a mechanical surface modification technology, which can extend the fatigue life of materials by introducing work hardening, compressive stress, and/or some additional microstructural change in surface layer resulting in a restraint of crack initiation and propagation on the surface. In this study, SUS304, which has high formability and corrosion resistance, was shot peened and fatigued for the determination of their effect on the evolution of microstructures. The fatigue of the specimens were carried out at three different cycles, followed by second shot peening and finish fatigue of 10⁶ cycles. The microstructures of the specimens were investigated using OM, EBSD, SED and EDS. The resulting mechanical property such as microhardness and residual stress was also investigated. Deformed layer of ~100μm and mechanical twins were observed after fatigue and shot peening test. The top surface layer of shot peened specimen showed the highest twin density and microhardness. The increase of the fatigue before shot peening caused increase and deepening of the compressive residual stress. However, the finish fatigue of 10⁶ cycles decreased overall compressive residual stress.

The Fe-Cr surface infiltrated layers on gray iron substrate were fabricated through a vacuum infiltration casting technique (VICT) using Fe-Cr alloy powder as raw materials. The microstructures of surface infiltrated layer, the macro-hardness and the micro-hardness distribution are investigated. The infiltrated layer includes a surface composite layer and a transition layer. The surface infiltrated layer was mainly composed of Cr2B, Cr2C3, FeSi, FeNi and Ni-Cr-Fe and solid solution. The main composition of transition layer was graphite, eutectic ledeburite, carbide and Fe-based solid solution. The macro-hardness of surface infiltrated layer is HRC52.8, and the macro-hardness of substrate is HRC16.22. The distribution of micro-hardness presents gradient change.

The microstructures of a series of ultra-low carbon (ULC) steels with various carbon contents (50-200ppm) and Ti addition (>500ppm) were studied by optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). The specimens were fabricated under the process of hot rolling, cold rolling and a two-step continuous annealing. The experimental results showed that the increase of carbon content decreased grain size, whereas the addition of Ti resulted in a larger grain size compared to those without Ti addition. Dislocation (cell) structures were introduced by cold rolling, but it was removed by the two-step annealing. Only MnS precipitated from the Ti-free specimens. However, a larger amount of fine TiN, a few coarse TiS and the extremely low number of much coarser Ti₃AlC were observed in the Ti-added specimens. Besides, the reduction of MnS inclusion was obtained by the addition of the Ti.

In this paper, Fe-Cr-B-Si-C alloy powers were used in laser direct manufacture single track laser cladding layer and thin wall cylinder. The microstructure, phase structure and mechanical properties of single track cladding layer and thin wall cylinder were investigated by optical microscopy (OM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and nano-indentation techniques. The results show that laser direct forming metal parts were fully dense, there were no defects such as crack and pore. There was somewhat grain coarsening in interlayer zone during laser processing, which will lead to weak mechanical properties. However, the whole properties of the thin wall cylinder may still satisfy the real part performance requirements. The change of laser scanning direction was beneficial to molten pool stirring, which lead to smash dendrite structure in favor of microstructure homogenization.

Low alloy Cr-Mo-V steels are usually used in steam power generation units. The evolution of the carbides often leads to embrittlement of the components during elongated service. Therefore, the determination of carbide evolution mechanism during long-time service is important to understand and prevent premature failures such as temper embrittlement. In this study, low alloy Cr-Mo-V steels used as main steam pipes in a thermal power plant were studied after various service times as well as in the as-fabricated condition. Electron microscopic analyses were carried out on extraction replicas to observe and analyze the morphology and composition of the carbides. Predominant plate-like vanadium-rich carbides were observed in the as-fabricated condition. When exposed to on-site service, the V-rich carbides transformed to Mo-rich carbides which have a typical H morphology. The change of morphology and composition of the carbide is mainly due to the gradual depletion of Mo from the solid solution. In addition, a non-destructive carbide extraction method was established for examination of the precipitates in the working turbine rotor.

Zinc oxide (ZnO) nanostructured surfaces can be reversibly altered from hydrophobicity to hydrophilicity in response to ultraviolet light or plasma treatment. In this paper, a thermal annealing procedure was used to tune ZnO nanowires' surface wettability, and the switchable reversible wettability was achieved. ZnO nanowires were synthesized by a simple solution method. The surfaces of as-synthesized ZnO nanowires demonstrated a superhydrophobicity with water contact angle of 151°. After a high temperature treatment (>300°C) for 20 minutes, their superhydrophobicity was transited to superhydrophilicity with water contact angle of < 10°. It was noted that this transition was very short (less than half minutes) when the annealing temperature is more than 400 °C. The high-thermal annealed superhydrophilic ZnO surfaces were recovered to superhydrophobicity after a low-temperature (~100 °C) procedure in 4 days. Thus, the tunable properties of ZnO surface energy result in reversible wettability between superhydrophobicity and superhydrophilicity. This tunable wettability can be explained based on ZnO as a semiconductor material, which provides different numbers of oxygen vacancies under different temperatures. This result will extend applications of ZnO nanomaterials to many important fields, such as microfluidic devices, chemical sensors and biosensors.

Nanostructured nickel sulfide as a cathode material for lithium ion batteries was fabricated. The large surface area of reaction between electrodes and electrolyte offers high energy density and capacity. Also, metal sulfides have high theoretical capacity. Nickel nanowires were fabricated by electrochemical deposition (ECD) using an anodic aluminum oxide (AAO) template with the diameter of 200 nm. Fabricated nickel nanowires were carried out with sulfuration treatment. The morphology and microstructure of the nanowires were characterized with FE-SEM, XRD, TEM and XPS. Nickel sulfide nanowires were applied for lithium ion batteries and charge/discharge tests were carried out with galvanostatic method.

The super-elastic Ti-50.8 at.% Ni alloy wires were tested under ultrasonic conditions using a self-designed ultrasonic fatigue tester. Different heat treatment processes were subjected to Ni-Ti wires in order to obtain different combinations of phase microstructure and corresponding mechanical properties. The fatigue behavior was evaluated under ultrasonic conditions. Experimental results show that proper thermo-mechanical treatment process increased the fatigue life of Ni-Ti wire obviously, because it could adjust the microstructure of Ni-Ti alloys, as well as the work-hardening effect. The longest fatigue life of Ni-Ti wire under ultrasonic conditions was obtained when it was annealed after cold drawing. The strengthen effect of heat treatment was attributed to the fine Ti₃Ni₄ precipitated phase, and the strengthen effect of cold drawing was attributed to the high density of dislocations. The SEM results show that smooth fractured faces with dimples existing in the propagation region of the fatigue cracks, indicating the excellent ductility and the resistance to the propagation of fatigue cracks of NiTi wires.

In the present work, the electrochemical behavior of Mg-xCe-1Zn (x = 3, 8 and 13wt.%) alloys have been investigated. The alloys were fabricated by using a vacuum induction melting method under an argon atmosphere. Potentiodynamic polarization was carried out in 3.5% NaCl solution of pH 7.2 at room temperature to evaluate the corrosion properties of Mg-xCe-1Zn (x = 3, 8 and 13wt.%) alloys. The microstructure of the Mg-(3, 8 and 13wt.%)Ce-1Zn alloys were mainly consisted of α-Mg and eutectic Mg₁₂Ce phase. With the increase of Ce contents, the volume percent and size of the eutectic Mg₁₂Ce phase were increased. Results indicated that the corrosion rate of Mg-xCe-Zn alloy was increased by the excessive Ce addition.

Theoretical calculations suggest that creating highly-oleophobic surfaces would require a surface energy lower than that of any known materials. In the present work, we demonstrate microtextured Al substrate surfaces with veins-like micro/nanostructures displaying apparent contact angles (CA) greater than 120°, even with nitromethane (surface tension γ₁ = 37 mN/m). The Al substrate was microtextured by a chemical solution mixed by zinc nitrate hexahydrate, hexamethyltetramine and a little of hydrofluoric acid. A fluoroalkylsilane (FAS) agent was used to tune the surface wettability. The Al substrates were microtextured by veins-like micro/nanostructures and generating a solid-liquid-vapor composite interface. Combination with FAS modification, the Al surfaces resulted in an oleophobicity with CA for nitromethane was 126.3° (152.7° for diethylene glycol, γ₁ = 45.2 mN/m). In addition, the Al surfaces demonstrated a low rolling-off angle with < 6° even for diethylene glycol. However, nitromethane droplet favored to pin on the sample surface even the sample stage is tilted to 90°. It is noted that this highly-oleophobic behavior is induced mainly by topography, which form a composite surface of air and solid with oil drop sitting partially on air. The results are expected to promote the study on self-cleaning applications, especially in the condition with oil contaminations.

Fe₃Al intermetallics were solidified separately in sodium silicate sand mould and permanent mould to get different cooling rates. After heat treatment (1000°C/15h homogenizing annealing + furnace cooling + 600°C /1h tempering + oil quenching), the microstructure, mechanical properties and impact fracture of Fe₃Al intermetallics were investigated. The microstructure of Fe₃Al intermetallics is refined and the dispersive second phase is more at higher cooling rate (in permanent mould) than that at lower cooling rate (in sodium silicate sand mould). Compared to intermetallics solidified at lower cooling rate, the Fe₃Al intermetallics solidified at higher cooling rate has the higher tensile strength and good hardness. The impact power increases from 35.28J to 59.09J, while the impact fracture transforms from intercrystalline fracture to intercrystallin+transcrystalline mixed fracture.

Considering the circle beam with even distribution of power density, an analytical model of single-pass laser transformation hardening is presented based on Green function. With the model, temperature profiles of the laser-heat affected zones of the samples are calculated to provide information about the depths of hardened zones.

In order to verify the validity of the model, experiments are carried out. In the experiments, a 1.5-kW continuous CO2 laser unit and ductile cast iron QT600-3 samples are used. The hardness distribution of the treated area of the sample is examined. There is a good agreement between the theoretical predictions and the experimental results.

Periodical boundary conditions (PBC) are important for the prediction of effective elastic stiffness of composites by applying the macro-microscopic asymptotic expansion homogenization method (HM). In this paper, two kinds of homogeneous periodical boundary conditions are proposed to satisfy the improved expression for the homogenized effective stiffness with the homogeneous characteristic function, and one is the relaxed periodical boundary condition, and the other is a precise polynomial derived from the first one. A typical example of the off-axis short-fiber reinforced composites is analyzed by the described procedure. The results show that the periodical boundary condition is not unique, and the relaxed periodic boundary condition is the simplest and most convenient method to guarantee periodical displacement and anti-periodical traction boundary conditions simultaneously in a widespread field with a unified form.

This paper aims to derive a cyclic visco-plastic constitutive model for API X80 steel based on the experiments and to develop FE analysis program to accurately simulate its cyclic/dynamic behavior. The tensile and low cycle fatigue behaviors for strain rate are characterized by the experiments. A three-dimensional FE simulation is developed using the cyclic visco-plastic model of API X80. Good agreement between analytical and experimental results clearly verifies the accuracy of the developed program.

This paper aims to determine the residual stress distribution of 600MPa grade high tensile strength steel pipe (STKT590) by girth welding. Welding FE simulation is achieved considering temperature dependent physical constants and mechanical properties, obtained by the temperature elevated tensile tests. Comparative analyses clarify the characteristics of residual stress profile near weld joint of STKT590 pipe.

Fe₃O₄/wood composite, a magnetic material, was prepared by In-situ chemosynthesis method at room temperature. The X-ray diffraction (XRD) shows that the average partical size of Fe₃O₄ was about 14 nm. The magnetic properties of the resulting composites were investigated by vibrating sample magnetometer (VSM). The composites have saturation magnetization (M_s) values from 4.7 to 25.3 emu/g with the increase of weight percent gains (WPG) of the wood for the composites, but coercive forces (H_c) are invariable, which is different from the magnetic materials reported before. It may be due to the fact that the interaction between wood and Fe₃O₄ becomes stronger when less of Fe₃O₄ particles are introduced in the composition, and this also changes the surface anisotropy (K_s) of the magnetism. A structural characterization by Fourier transform infrared (FTIR) proved the interaction between Fe₃O₄ particles and wood matrix, and it also illustrates that this interaction influences the coercive force of the composite.

The purpose of this paper is to investigate the influence of cohesive zone model (CZM) on the mechanical properties of CNTs-composites with debonding interface, and the finite element computation is carried out by the ANSYS software with CZM. The CZM model represents the interface separation and traction using three parameters derived from a surface potential function, and the effective plastic strain and stress concentration factor are calculated for the models with and without cohesive zone. It is obviously found that the effective plastic strain increases and the stress concentration factor decreases with the application of CZM, and it is reasonable to improve the mechanical properties of CNT-composites with debonding interface by applying the CZM.

The microstructures and mechanical properties of as-cast Mg-Zr-Ca alloys were investigated in this study for potential use in biomedical applications. The Mg-Zr-Ca alloys were fabricated by commercial pure Mg (99.9 mass%), Ca (99.9 mass%), and master Mg-33mass%Zr alloy. The microstructures of the alloys were examined by X-ray diffraction (XRD) analysis and optical microscopy (OM), and the mechanical properties were determined from tensile tests. The experimental results indicate that an increase of Zr obviously increases the strength of Mg-Zr-Ca alloys with 1 mass% Ca and the formation of Mg₂Ca decreases the strength of the alloys. Mg-1Zr-1Ca alloy (mass%) has the highest strength and best ductility among all the studied alloys.

Polyethylene (PE) film was coated with polyurethane/nanosilica composite layer using rod Mayer process. The polyurethane/nanosilica system was prepared by dispersing nanosilica powder into solvent borne polyurethane (PU) binder under vigorous stirring. The silica nanoparticle used has an average diameter of 16 nm, and their weight fraction were varied from 0 % to 14 %. Two different thicknesses of the PU/nanosilica coating layer were fabricated which were about 4 μm and 8 μm. The structure and thermal mechanical features of the nanocomposite coated PE film were characterized by scanning electron microscope (SEM), dynamic mechanical analyzer (DMA), thermogravimetric analyzer (TGA) as well as tensile tests. The results showed that thin layer coating of the PU/nanosilica composite reduced tensile strength of PE substrate slightly. However, the nanocomposite coating of up to 8 μm reduced the elongation % of PE substrate significantly. PU/nanosilica composite coating layer increased the tensile modulus and stiffness of PE substrate. There was no influence of the PU/nanosilica composite coating to the thermal degradation rate of PE film.

1 wt.% different rare earth elements (Ce, Y, Gd, misch metal, Nd) are added into the alloy of Mg-6Li-1.5Al, respectively. The different effects on the microstructure and mechanical properties are evaluated. The additions of these elements produce granular and rod-like precipitated phases, which are Al₂Ce, Al₂Y, AlGd, Al₃La, Al₂Nd, respecitvely. All the rare elements have refining effects in the alloys. Misch metal and Nd have the best refining effects, while Y and Ce have the least obvious refining effects. All the elements are favorable for the improvement of strength and elongation. Mg-6Li-1.5Al-1Ce possesses the highest strength, and Mg-6Li-1.5Al-1Y possesses the highest elongation. If considering the different yield of elements, Mg-6Li-1.5Al-1Y possesses both the highest strength increase per rare earth yield and elongation increase per rare earth yield.

Bioceramic composites were synthesized by sintering the powders of hydroxyapatite (HAp) mixed directly with additive of 5.0wt.%SiO₂ at different temperatures ranging from 800°C to 1200°C. X-ray diffraction analysis indicated that the phase transformation from HAp to tricalcium phosphate (TCP) began to take place as the sintering temperature is as high as 900°C, and the content of TCP phase increased notably with increasing temperature. Microstructural observations demonstrated that a distinctive microstructure featuring crystalline clusters with different sizes surrounded by glassy matrix formed in HAp-5.0wt.%SO₂ bio-composites, as the sintering temperature reached 1100°C. Soaking experiments in a stimulated body fluid revealed that the bio-composites showed a faster bone-like apatite layer growth, namely an enhanced in vitro bioactivity, as the sintering temperature increased, since the increase in sintering temperature promoted the phase transformation from HAp to TCP, which exhibits a higher solubility than HAp.

High cycle fatigue (HCF) property of one kind of near alpha titanium alloy named after Ti-600 was investigated at a frequency of 120~130Hz and with a load ratio R of 0.1. The HCF strength for the alloy at ambient temperature was found to be 475MPa. The observed high HCF strength was attributed to its overlapping plate like α+β phase microstructure. At the same stress of 600MPa, the distance between two fatigue stripes for the sample fractured at 8.61×10⁵ cycles was wider than that of the sample failured at 1.78×10⁶ cycles, which indicated that their propagation resistance for fatigue cracks was smaller.

Based on the theory of deformation-induced ferrite transformation (DIFT), effect of different controlled-rolling and controlled-cooling process on the microstructure and mechanical properties of the low alloy steel 2.25Cr1MoNb were investigated and the mechanism was discussed. Simulation experiments of hot deformation were carried out with the Gleeble-1500 system. Specimens were deformed compressively by single-pass and multi-pass hot rolling process with different deformation temperature, deformation reduction, and cooling rate. Results show that the ferrite grain size decreased and the ferrite volume fraction increased with decreasing deformation temperature. Higher deformation reduction resulted in finer ferrite grain size and higher ferrite volume fraction. When the cooling rate increased, ferrite grain size decreased but the ferrite volume fraction did not change much. The grain size and the ferrite volume fraction were improved more obviously by multi-pass than single-pass rolling. Results also showed that both the tensile strength and elongation of the steel were improved obviously when the grain size decreased. We may conclude that DIFT technique can improve the mechanical properties of the test material obviously.

The effect of Fe addition on the cycle performance of FeS₂cathode for Li/FeS₂cell was investigated. After cathode fabrication, additional compounds were not formed. In the case of Li/FeS₂ cell without Fe, a large voltage drop was observed at initial discharge process. Also, the cell showed poor cycle performance until the 40th cycle. On the other hand, the Li/FeS₂ cell with 10wt.% Fe delivered a higher the 1st discharge capacity of about 670mAh/g-FeS₂ and it exhibited better cycle performance than the cell without Fe. Moreover, rate capability of the cell was improved by the addition of Fe in the FeS₂cathode.

The microstructure and texture of cold rolled low carbon steel produced by compact strip production after batch and continuous annealing have been investigated. Optical microscopy, bulk X-ray texture analysis and micro orientation analysis with Electron Back-Scattered Diffraction (EBSD) were conducted to investigate the general microstructure and texture in correlation with the mechanical properties as well as formability under the two annealing procedures. The results indicate that the microstructure of the cold-rolled steel after batch annealing exhibit special orientation relationship with the matrix in comparison to continuous annealing. As an explanation of the oval-shaped grains character, the recrystallization microstructure and texture evolution was discussed. It is concluded that the annealing plays a significant effect on the special orientation and texture formation of the CSP strip, and thus to the formability and mechanical behavior of the final products.

Both thermally induced and stress-driven segregation behavior of P, Mo and Cr were experimentally studied in steel 2.25Cr1Mo. The relationship between Mo and P, Cr and P were analyzed. Results of specimens solution treated at 1050°C and held at 540°C show that the concentration of Mo at grain boundary increased with increasing concentration of P during aging, and that the experimental data dots of Mo and P relationship were distributed in a linear zone, whereas, the data dots of Cr and P relationship were scattered. It is concluded that the non-equilibrium grain boundary co- segregation (NGCS) of Mo and P occurred, and the NGCS of Cr and P did not occur during aging in steel with the above heat treatment history. Results of tension test show that both the NGCS of Mo and P, and NGCS of Cr and P occurred under low stresses 30MPa at 500 °C. And the typical multi-elements NGCS of P-Mo-Cr occurred during aging. It is clear that the three elements P, Mo and Cr in steel 2.25Cr1Mo are interactional and inter-promoted.

The (Cu₄₂Zr₄₂Al₈Ag₈)_99.5Si_0.5 bulk metallic glass (BMG) rods, 3 mm in diameter, with different fraction of nanocrystalline phase were prepared by isothermal annealing the as-cast BMG rods at the temperature within the supercooled temperature region for different time period in vacuum, respectively. The result of hardness and compression test revealed that the hardness and yield strength of compression test all exhibits an increasing trend with crystallization fraction. The maximum 1990 MPa yield strength, 2100 MPa fracture strength, and 5 % failure strain occurs at the 50% crystallized BMG sample (with an average size about 60 nm). This suggests that these homogeneous distributed nanocrystals which embedded in the amorphous matrix may act as a network obstacle in the glassy matrix to restrict the propagation of highly localized shear-banding, avoiding catastrophic shearing-off through the whole sample and result in improving the plasticity.

Samples of pure Cu cylinder were plastically deformed by combination of cold-forging (CF) and cold-drawing (CD) under the liquid nitrogen temperature (LNT). X-ray diffraction measurements indicate that an increase of deformation strain leads to a decrease in crystallite size and an increase in twin densities for the CF and CD processed ultrafine-grained (UFG) samples. Dynamic recovery is suggested to start during the deformation process, and leads to a decrease of dislocation density at large deformation strains. The increase of twin density could compensate the loss of microhardness because of the decreasing of dislocation density. The electrical conductivities of CF+CD samples were tested through standard four-probe method, all of which are higher than 92% IACS. The results suggest that the strength of pure Cu could be improved and still keep its relatively high electrical conductivity by introducing deformation twins (DTs) into its microstructure.

The microstructure and room temperature (RT) mechanical properties of the Ni-15Si-2Nb-1Cr-3Ti-0.2B alloy were investigated by means of X-ray diffraction, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and tensile test in air and vacuum. The results of tensile test revealed that the effect of Ti addition can significantly improve the elongation as well as ultimate tensile strength (UTS) (18.3% and 1320 MPa in air, 21% and 1600 MPa in vacuum) in comparison with the Ni-18Si-3Nb-1Cr-0.2B base alloy (10% and 1130 MPa in air, 14% and 1240 MPa in vacuum) at room temperature. In addition, the fracture surface of specimen after tensile test presents a typical transgranular ductile mode, with a fully dimpled fracture pattern. This indicates that the addition of Ti in the Ni-15Si-2Nb-1Cr-3Ti-0.2B alloy can effectively suppress the environmental embrittlement at room temperature. In addition, the Ni-15Si-2Nb-1Cr-3Ti-0.2B alloy exhibits insensitively to the strain rate both in air or vacuum at room temperature.

Effects of Zr/Ti substitution for Fe on the magnetic properties, phase evolution, and microstructure of directly quenched Nd_9.5Fe_72.5Ti_3-xZr_xB₁₅ (x=0-3) bulk magnets of 0.9 mm in diameter have been investigated. Proper Zr substitution for Ti has been found to well-modify phase constitution and refine the grain size from 200-250 nm to 50-100 nm. Consequently, the magnetic properties of the rods are enhanced remarkably from _iH_c= 6.2 kOe and (BH)_max= 5.6 MGOe for Zr-free rod to _iH_c = 9.2-13.5 kOe and (BH)_max= 6.9-8.2 MGOe for Zr-substituted Nd_9.5Fe_72.5Ti_3-xZr_xB₁₅ rods (x = 0.5-2). The optimal magnetic properties of B_r = 6.6 kG, _iH_c = 9.6 kOe and (BH)_max = 8.2 MGOe can be achieved for the directly casted Nd_9.5Fe_72.5Ti_2.5Zr_0.5B₁₅ alloy.

The oxide coatings were prepared on T6-tempered A16061 alloys substrate under a hybrid voltage (AC 200V-60Hz & DC 260V value) in an aluminate electrolyte by plasma electrolytic oxidation (PEO) in 5, 10, 15, 20 and 30 min, respectively. X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the coating microstructure. XRD analysis results show that the coatings consist of α- and γ-Al₂O₃. The abrasive behaviors of the oxide coatings in different PEO-treated times were tested assessed by conducting dry ball-on-disk wear tests. The abrasive weight loss increased when the PEO-treated time increased, and finally became equilibrium.

To improve temperature-sensitivity of conventional poly(N-isopropylacrylamide) (PNIPAM) hydrogel, a kind of lyotropic liquid crystal based on polyoxyethylene 20 cetyl ether (Brij 58, C16E20) was used as template to prepare nanostructured hydrogel. The structure, morphology swelling behavior and temperature-sensitivity of confined PNIPAM hydrogel were characterized. SEM images showed that polymerization of N-isopropylacrylamide (NIPAM) in Brij 58 solution formed hydrogel with honeycomb structure. Compared to pure PNIPAM hydrogel, the swelling rate increases. The time for losing water was greatly shortened. The thermal-responsibility measured by differential scanning calorimeters (DSC) was improved remarkably. Finally, as for oscillatory swelling/deswelling behaviors, rapid recovering could be found by alternating temperature from 20 to 37°C.

Carbon nanotubes (CNTs) have attracted considerable interest because of their unique physical, electrical properties and many potential applications. Carbon nanotubes are considered to be the most promising candidate in electrode materials for secondary battery, solar cell and supercapacitor. Non-conductive substrates, such as silicon wafers have usually been used to synthesize CNTs. However, in applications such as electrodes, it is desirable to have CNTs grown on conductive buffer layer and conductive substrates. We researched the fabrication of carbon nanotubes on Ni/TiO₂/Ti substrate by Thermal chemical vapor deposition (TCVD). Experimental parameter is synthesis temperature, time and buffer layer thickness. The samples were characterized by means of field emission scanning electron microscopy (FE-SEM), Raman spectroscopy analysis, transmission electron microscope (TEM) and electrochemical test. The synthesized CNTs have the diameter of about 100~200 nm and the length of about 5~10 μm. Li/CNTs cell with CNTs on Ti substrate exhibited good charge/discharge behavior and slow capacity fading.

4-benzyloxyl-3-methoxylbenzaldehyde-copolystyrene resin, a novel functional polymer material, was synthesized. The reaction of cross-linked chloromethylated polystyrene (1%DVB, 1.24mmolCl/g) with 4-hydroxyl-3-methoxylbenxaldehyde was performed under phase transfer catalyzed condition, in which DMF was acted as solvent, and K₂CO₃ as solid base, leading to the formation of 4-benzyloxyl-3-methoxylbenzaldehyde-copolystyrene resin. The effect of various phase transfer catalysts including PEG-400, 18-crown-6 ether, CTMAC, TBAC, and TBAI was investigated. Final products were characterized by FTIR and elemental analysis. The results obtained confirm that phase transfer catalytic synthesis of 4-benzyloxyl-3-methoxylbenzaldehyde-copolystyrene resin is a facile and effective method.

Magnesium alloys are attracting increasing research interests due to their low density, high specific strength and good machinability and availability as compared to other structural materials. However, the deformation and failure mechanisms of nanocrystalline Mg alloys have not been well-understood. In this work, the deformation behavior of nanocrystalline Mg-5% Al alloys was investigated using compression test, with a focus on the effects of grain size. The average grain size of the Mg-Al alloy was changed from 13 μm to 50 nm via mechanical milling. The results showed that grain size had a significant influence on the yield stress and ductility of the Mg alloys, and the materials exhibited increased strain rate sensitivity with decrease of grain size. The deformation mechanisms were also strongly dependent on the grain sizes.

The formation enthalpies of Al-Ga-In, Al-Ga-Sn, Cd-Ga-Sn and Ga-Sn-Zn liquid alloys are calculated by molecular interaction volume model (MIVM) using only the coordination numbers and the binary infinite dilute enthalpies. The predicted values are compared with the experimental data, the results indicate that the model is reliable as well as convenient.

Anatase TiO₂ aqueous sols were prepared below 70 °C by sol method. The influences of preparing conditions on the crystal structures and stability of the sols were investigated with X-ray diffraction (XRD) and Zeta potential. The photocatalytic activities of the anatase TiO₂ aqueous sols were characterized by degradation of methyl orange and methylene blue under ultraviolet light, fluorescent light and sunlight. The sols demonstrate higher photocatalytic activity than that of Degussa P25-TiO₂.

Superior hole-mobility and compatibility with mainstream Si processing technology make strained SiGe an attractive channel material for p-MOSFET. In this paper, the electrical characteristics of strained Si_1-xGe_x channel p-MOSFET with various Ge mol fraction are studied via 2-D numerical simulation by ISE TCAD simulation software. The results indicate that the Ge mol fraction affects electrical characteristics of the device significantly. With the increase of Ge mol fraction, remarkable increase occurs in the sub-threshold current, while the sub-threshold swing is stable. At the same condition, increment of the gate capacitance in strained Si_1-xGe_x p-MOSFET is slower gradually. Also, the threshold voltage shows a linear function of the Ge mol fraction.

Nano-sized hard materials have to be developed for improving mechanical properties. Nowadays, high energy mechanical milling (HEMM) method is widely used to fabricate nano-sized powders. The mechanical properties increase with decreasing grain size. However, grain growth has occurred by conventional sintering method with long sintering time. In this work, high-frequency induction heated sintering (HFIHS) was used to fabricate highly dense nano-sized WC-10vol.%Nicrobraz 30, 150 and LC composites for short sintering time without grain-growth. Therefore, control of grain growth during sintering is one of the keys to the commercial success of nano-structured cemented carbide composites. After sintering, relative density of WC-10vol.%Nicrobraz 30, 150 and LC composites were 99.9%, 98.7% and 98.0%, respectively. The grain sizes confirmed that full-width at half maximum (FWHM) was used from the result of XRD. The highly dense nano-sized WC-10vol.%Nicrobraz 30, 150 and LC composites were fabricated successfully using HEMM and HFIHS equipments.

The effect of equal channel angular pressing (ECAP) on high-temperature compressive deformation and damage behavior of LY12 Al alloys was studied. It is found that the ECAP and temperature have noticeable effects on the compressive deformation and damage behavior of the LY12 Al alloys, especially in the case that the testing temperatures are near and above recrystallization. With the increase of ECAP passage, grains are refined significantly and the plastic deformation ability of the LY12 Al alloys is thus enhanced obviously. With increasing compressive temperature, obvious grain coarsening occurs in ECAPed samples and the plastic deformation capacity is greatly strengthened.

The effect of different surface energies of substrate on adhesive bonding at room temperature is investigated in this paper. Comparing to the RCA cleaning procedure, the improved cleaning procedure increases surface energies of wafers which were detected by water contact angle (WCA) measured with JY-82 contact angle goniometer. This higher surface energy leads to stronger bonding properties between Si and glass with epoxy (TS814) at room temperature. The bonding strength was detected by Series IX Automated Materials Testing System. Compared with the RCA cleaning simples, the one with high surface energy of wafers reached 8.56Mpa, more than seven times stronger than the others.

Effects of annealing on the evolution of self-assembled Ge/Si (100) islands grown by ion-beam sputtering were investigated by atomic force microscopy. The islands with high aspect ratio (0.2-0.33) and small diameter (45-75 nm) without annealing were observed. Significant evolutions occur on islands number density, shapes and aspect ratio with the changes of the annealing time and Ge coverage. Increasing annealing duration, the density and aspect ratio decreased with a simultaneous increase of the average volumes at low deposition coverage. Comparing with it, the density and aspect ratio increased during the annealing of the samples with high deposition coverage. No pyramid islands were observed in our samples. Atom diffusion and the poor crystalline Si buffer confirmed by the Raman spectrum measurement led to these results.

Magnesium alloy is a promising candidate for use as biodegradable implant material. However, its corrosion rate is too fast in human body fluid. Thereby, improving corrosion resistance is an urgent problem for application of the magnesium alloy in the medical field. Presently, Mg-8.0Al-1.0Zn-xGd alloys were prepared. Effect of rare earth Gd on the microstructures and corrosion resistance of magnesium alloy were investigated. Results showed that the most of Al₃Gd particles, a high melting point rare earth compound, are distributed in β phases (Mg₁₇Al₁₂). With the increase of the content of Gd, the amount of precipitation of β phases increased and interconnected each other. Fine network-like β phases acted as corrosion barrier and effectively impeded the corrosion extending. The corrosion resistance improved with the increase of rare earth Gd.

The orthogonal perovskite EuFe_0.9Co_0.1O₃ oxides with uniform particle size distribution were prepared by a sol–gel method. The samples were calcined at the different temperatures and the results showed that the mean grain size increased from 31 to 38 nm when the calcinations temperature increased from 600 to 900 °C. The investigation of sensing properties exhibited that the sensor based on EuFe_0.9Co_0.1O₃ calcined at 800 °C has good gas sensing properties to acetone gas at the operating temperature of 280 °C.

A new and facial method to directly synthesize stable and crystalline pure phase Ni(OH)₂ nanosheets was developed using cationic surfactant (cetyltrimethylammonium bromide, CTAB). The advantages of the method are facile synthesis, at low temperature (room temperature and 60 °C), and low cost. The results revealed that all the products were flake-like nanosheets with typical length in the range of several hundreds nanometers and width in the range of several to several tens nanometers. A possible formation mechanism is preliminary proposed for the formation of the nanostructure. It is considered that this simple aqueous solution synthetic route can be applied as a general method for the preparation of other metal hydroxides with nanosheets.

Because laser cladding is a multi-variable coupling process, the relation between clad bead and process parameters is non-linear with multi-objects and multi-variables. Moreover, it is very difficult to find out an exact analytic model to express this relation. In this study, a neural network model, which is often used for non-linear problems, is developed to explain the relationship between process variables and clad parameters (the width and height of cladding bead). Some samples obtained in experiments are used to train the network model to form the perfect map relation between input and output, and other samples are employed to test the network model. A normal BP algorithm and an amend BP one are trained, and it is found that the amend BP algorithm has advantages over the normal BP one. The experimental results agreed well with those calculated with the neural network model, which indicates that the developed BP neural network prediction model is feasible and valid in theory and in practice.

In this work, the influence of Y³⁺ doping on the phase transformation and photoluminescence properties of Gd₂O₃:Eu³⁺ red phosphor was studied. Red-emission (Gd_0.95-xY_xEu_0.05)₂O₃ phosphor particles have been processed via homogeneous precipitation precursor synthesis followed by calcination at 1300 °C for 4h. The resultant oxides could be modulated from a pure monoclinic phase to a pure cubic phase by Y³⁺ doping. The phosphor with a cubic structure shows a significantly stronger red emission, and a blue shift of the charge-transfer band (CTB) was observed on the excitation curve by Y³⁺ doping. These phenomena have been deciphered by considering structural features of the products.

In this paper, a measurement strategy for laser-hardened width was presented. The hardened zone is determined by the temperature distribution of the workpiece, and the temperature of object affects the gray value of images obtained in laser hardening. A color CCD was used to take the heat radiation images in real-time during laser transformation surface hardening. Detection system software was developed on the Visual C++, with which the different temperature distribution was displayed clearly and then the hardened width was obtained by image processing and threshold segmentation.The detection system, which maybe serve quality control for laser hardening, was verified experimentally.

A 2D microstructure and solute microsegregation model of Al-Si-Cu ternary alloys is presented by using cellular automaton(CA) method. In CA model, an improved algorithm was presented that abandoned the assumption of solid/liquid interface position and velocity so as to calculate the solid fraction in the solid/liquid interface unit. Then, using CA model, a dendrite of Al-Si-Cu ternary alloys is simulated. Finally, solidification microstructure and solute microsegregation are simulated, and the simulated results can reflect the microstructure and different solute microsegregation during solidification process.

A shear-lag model is developed for carbon nanotube-reinforced magnesium matrix composites using the Micromechanics. The main morphological features of the nanocomposites are captured by utilizing a composite cylinder embedded with a capped nanotube as the representative volume element. The Micromechanics is employed to determine the effective Young's modulus of carbon nanotube reinforced composites based on its Microstructure. The capped nanotube is equivalently represented by an effective fiber having the same diameter and length but different properties of Young's modulus, which is determined from the Components of the composites.

Al₂O₃ coatings were prepared on Al6061 alloy substrate under a hybrid voltage by plasma electrolytic oxidation in a silicate electrolyte. Potentiodynamic polarizations tests had been carried out in 3.5wt% (0.6M) NaCl water solutions under static conditions to evaluate the corrosion performance of the coated or uncoated samples. A double-layer Al₂O₃ coating consisted of γ- and α-Al₂O₃, formed upon the Al alloy substrate. It is shown that the Al₂O₃ coatings on Al6061 alloy play roles of anticorrosive coatings, and proper treating time is suitable to enhance the corrosion resistance of the Al₂O₃ coatings.

This letter reports a synthesizing method with an enhanced solid state reaction to fabricate SnO₂ nanorods. The structure and morphology of SnO₂ nanorods were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the nanorods were rutile SnO₂ with the diameter of about 30 nm and the length of several micrometers. It was found that the chlorine salt was very important for controlling the grain size of nanoparticles and providing kinetic and ambulatory circumstance to induce oriented growth of SnO₂ nanoparticles. The growth mechanism of the nanorods can be understood on the basis of oriented aggregation induced by polar forces.

X-ray diffraction (XRD), Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and magnetic measurement system were used for investigating the microstructure and magnetic properties of melt-extracted Co_68.15Fe_4.35Si_12.25B_15.25 microwires with diameters of 52 μm and 83 μm for potential applications. Experimental results indicated that as-cast wire with 52 μm was entirely amorphous characteristic, while partial nano-crystalline structure including regularly atomic arrangement in microregions could be observed in 83 μm wire. There was a transform of increased coercivity and decreased magnetic permeability with an increasing diameter, resulting from the magnitudes of the magnetic anisotropy induced by the residual inner stress and magneto-crystalline anisotropy. It can therefore be concluded that the 52 μm wire has better magnetic properties, is more suitable for potential applications in magnetic field sensors.

The filming on steel using the disproportionation reaction of sub-sulphide of Al was studied. The chemical vaporization depositions were realized using (2Al₂O₃+6C+Al₂S₃) or (4Al+Al₂S₃) as reaction mixture at 1100°C and the pressure of 5 Pa. It is indicated that the coating formed by evaporation of (2Al₂O₃+6C+Al₂S₃) consists of α-Fe and Al₁₃Fe₄, possesses thin diffusion layer and dark rough surface, and is resistant to solution of nitric acid with alcohol; But the coating formed by evaporation of (4Al+Al₂S₃) consists of Fe₃Al and AlFe, and possesses thick diffusion layer and bright smooth surface.

The microstructure and properties of super martensitic stainless steel (SMSS) microalloyed with tungsten and copper were studied by means of optical microscopy, dilatometer, X-ray diffraction, and tensile tests. The results showed that the microstructure of SMSS, after quenching and tempering, was a typical biphase structure with tempered martensite and reversed austenite dispersedly distributed in the martensite matrix. W and Cu were added into the SMSS to reduce the transformation temperature (Ms) and improve the strength and hardness of the matrix by grain refining and solid solution strengthening. Thermocalc calculations confirmed that M₂₃C₆ compound and Laves phase were precipitated during tempering in the investigated steel. Compared with the traditional SMSS, the steel microalloyed with W and Cu performed better mechanical properties.

Titanium alloys are expected to be much more widely used for hard tissue implant materials due to their superior biocompatibility and high corrosion. However, the larger Young's modulus of present titanium alloys always leads to stress shielding and harmful effects on human bones and results in premature failure of the implant. Recently a d-electron alloy design method has been proposed to design low elastic modulus titanium alloys and achieve some actual results. In this paper, a series of the Ti-Nb-Zr alloys has been designed with the d-electron alloy design method, and the phase structure, lattice parameter and elastic modulus have been investigated. The results show that with the increase of and , the lattice parameters of these alloys increase monotonously with the single phase structure of bcc β phase. The maximum increment reaches 4.5% compared with that of matrix β phase. As the and increase up further, the phase structure begins to change from bcc β phase to hcp α phase. Correspondingly the elastic modulus decreases first and then increase, from 96.8 GPa to 67.4 GPa, and then to 83.2GPa with the increase of and . The lattice parameter and phase structure both exhibit significant influences on the elastic modulus of these alloys.

Consisting of a CCD camera, a frame grabber and a computer, a system is developed to monitor the molten pool parameters in laser cladding. The molten pool images, grabbed by the CCD camera, are processed by the software, and then the geometry and temperature field distribution of molten pool are measured, which can show the changes in laser cladding. The relationship between the molten pool parameter and the visible defects is revealed, and the visible defects can be detected in-time by diagnosis of the molten pool parameters.