International Journal of Modern Physics B

Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in the γ-Fe temperature region were investigated using carburizing technology. The carbon penetration profiles from the iron surface to interior were measured by field emission electron probe microanalyzer. The carbon diffusion coefficient in pure iron carburized with different magnetic field intensities was calculated according to the Fick's second law. It was found that the magnetic field intensity could obviously affect the carbon diffusion coefficient in pure iron in the γ-Fe temperature region, and the carbon diffusion coefficient decreased obviously with the enhancement of magnetic field intensity, when the magnetic field intensity was higher than 1 T, the carbon diffusion coefficient in field annealed specimen was less than half of that of the nonfield annealed specimen, further enhancing the magnetic field intensity, the carbon diffusion coefficient basically remains unchanged. The stiffening of lattice due to field-induced magnetic ordering was responsible for an increase in activation barrier for jumping carbon atoms. The greater the magnetic field intensity, the stronger the inhibiting effect of magnetic field on carbon diffusion.

Porous metal fiber media (PMFM) is a kind of advanced structural and functional material, and it has attracted a wide spread attention owing to excellent sound absorption performance. The sound absorption property of PMFM is mainly influenced by the fiber diameter, the average pore size and thickness of PMFM. In the paper, three stainless steel fibers with the diameters (∅) of 8, 12 and 20 μm were used to make PMFM with the average pore sizes of 10, 20, 30 and 40 μm and the thicknesses of 1, 2 and 3 mm by air-laid and sintering processes. The sound absorption coefficients of PMFM were tested in impedance tube using two-microphone transfer-function method according to ISO 10534-2 and ASTM E1050-98 international standards at room temperature. The results show that when the frequency ranges from 50 Hz to 6,400 Hz in material with the average pore size of 20 μm and the thickness of 3 mm and the fiber diameter of ∅8 μm, the average sound absorption coefficient is the highest.

CaCu₃Ti₄O₁₂ (CCTO)–poly(vinylidene fluoride (PVDF)) composites were prepared by melt blending and hot molding techniques. The addition of CCTO remarkably enhanced the dielectric properties and the thermal conductivity of PVDF composites, while the melting point of the PVDF composites (~170°C) was almost independent of the CCTO concentration. Based on the results of dielectric constant and dielectric breakdown voltage, the PVDF composite containing 40 vol.% CCTO fillers shows the optimized capacitive energy storage potential (7.81 J/cm³).

In this paper, Ti-6Al-4V alloy rods were manufactured by the powder compact extrusion of a powder mixture of hydride–dehydride (HDH) titanium powder, elemental aluminum powder and master alloy powder. Extrusions were carried out at 1300°C and with a holding time of 5 min in an argon atmosphere. The effects of different heat treatments (HT1: 960°C/1 h, water quenching, HT2: 960°C/1 h, water quenching + 500°C/6 h, air cooling, HT3: 850°C/2 h, furnace cooling to 540°C, then air cooling) on the microstructure and mechanical properties of as-extruded Ti-6Al-4V alloy rods were investigated. The results showed that a homogeneous microstructure, composed of a lamellar structure with a grain size range of 40–60 μm, was produced by powder compact extrusion of a powder mixture. The mechanical properties achieved were an ultimate tensile strength (UTS) of 1254 MPa, a yield strength (YS) of 1216 MPa and 8% ductility. After quenching at 960°C and with a holding time of 1 h, the UTS and YS of the heat treated Ti-6Al-4V alloy rod were increased to 1324 MPa and 1290 MPa, and the ductility was increased to 12%. After HT2, the UTS and YS of the heat treated Ti-6Al-4V alloy rod were significantly increased to 1436 MPa and 1400 MPa, but the ductility decreased to 4%. After HT3, the mechanical properties of the heat treated Ti-6Al-4V alloy rod were slightly decreased to give a UTS of 1213 MPa and a YS of 1180 MPa, with an increase in ductility to 11%. The microstructural changes of as-extruded Ti-6Al-4V alloy rods were also investigated for the different heat treatments.

Impurity control is crucial to Ti metal powder injection molding (Ti-MIM) since titanium is a universal solvent to interstitial elements such as oxygen, carbon and nitrogen. In this study, a low decomposition temperature binder system was developed; the rheological and solvent debinding assessments of the feedstock formulated from this binder were performed. Solvent mixing was employed to prepare homogeneous feedstocks. Effects of powder shape and solid loading on rheological properties were evaluated. After injection molding, a debinding profile was constructed. The debound parts were then characterized by microstructural observation.

Bimetallic structure of nanoparticles is of great interest due to their extraordinary properties, especially in combining the specialty of the core and its shell. This work reports the effect of pH on the synthesis of Ni–Au (nickel–gold) bimetallic nanoparticles. The synthesis involves a two-step process where Ni nanoparticles were first synthesized using polyol method with hydrazine as the reducing agent. This was followed by the process of reducing to Au in the solution containing pre-prepared Ni to form Ni–Au bimetallic nanoparticles using sodium citrate as the reducing agent. The results obtained from Transmission Electron Microscopy (TEM) show that the process can possibly produce either core-shell structure, or mixture of Ni and Au nanoparticles. Magnetic property of core-shell structure investigated using Vibrating Sample Magnetometer (VSM) demonstrated typical characteristic of ferromagnetic with an increased magnetization as compared to Ni nanoparticles. The saturation magnetization (M_s) and coercivity (H_c) were obtained as 19.1 emu/g and 222.3 Oe, respectively.

The inhomogeneity on texture, microstructure and magnetic properties of hot deformed (HD) disc shape R₂Fe₁₄B-typed magnets along radial and axial directions has been investigated. HD disc shape NdFeB magnet exhibits inhomogeneous texture, grain morphologies and magnetic properties not only along the radial direction but also along the axial direction. Higher magnetic properties can be found in the middle part of the HD magnet, due to the existence of larger volume fraction of plate-like Nd₂Fe₁₄B grains and the well c-axis alignment parallel to the pressing direction. In addition, particle-like and coarser grains are easily found not only in the bottom but also in the edge of the HD magnet, which may degrade the magnetic performance of the samples cut from those parts. Owing to the inhomogeneity of (00L) texture and grain morphologies along axial and radial directions, the optimal magnetic properties of B_r = 12.7 kG, H_ci = 5.1 kOe and (BH)_max = 39 MGOe can be obtained only in the middle sample of HD magnet with slight polishing the top and bottom surfaces.

Ni–Co coatings are widely used due to their unique mechanical properties, high anticorrosion properties, good thermal stability and special magnetic properties. Ni–Co–xTiO₂ (x = 0–20 g/L in the electrolyte) composite coatings were fabricated by electrodeposition on mild steel. The effect of TiO₂ concentration on the microhardness, surface morphology and tribological behaviour has been studied. The results show that, comparing with pure Ni–Co coating, both microhardness and wear property of the Ni–Co–TiO₂ composite coatings were significantly improved. The microstructure and properties for the Ni–Co–TiO₂ composite coatings were varied following with the TiO₂ concentration. The mechanism of mechanical property improvement was also discussed.

In this paper, ingot breakdown process of a high Nb containing TiAl alloy with a chemical composition of Ti–42.63Al–8.11Nb–0.21W–0.09Y (at.%) has been investigated under conventional forging conditions. It was found that the present alloy possesses superior hot-workability that can be successfully forged by conventional upsetting route due to the appearance of large amount of β/B2 phase, though shear band was observed in the forged-pancake. Further studies revealed that hot-working performed in (α + β) phase region which can effectively impede the β → α transformation and thus significantly increase the volume fraction of β/B2 phase. In contrast, the amount of β/B2 phase was notably reduced by heat treatment at the same conditions. This stress-induced effect is considered to be responsible to the superior hot-workability of the present alloy and the mechanism has been discussed and reasonably clarified. It was also suggested that the stress-induced effect has practical significance that it allows the implementation of conventional multi-step forging process which can develop fine and uniform microstructures suitable for secondary processing.

Zn and Zn–Bi coatings were electroplated on mild steel substrate by direct and pulse current (PC) techniques. The effects of Bi and deposition method on the phase, microstructure and mechanical properties of Zn-based coatings have been studied. Results showed that the crystal orientation and microstructure of Zn–Bi coatings were different compared to the pure Zn coating. By adding a small amount of Bi solution into Zn electrolyte, the microhardness of Zn–Bi coatings was increased by two times, and the wear volume loss was also decreased. Finer grain size and smoother surface can be achieved by utilizing PC deposition, resulting in better mechanical properties compared to the direct current (DC) deposition.

The relationship between microstructure and mechanical properties in cast aluminum alloys is complex and is strongly affected by the casting process conditions and melt handling practices. The aim of the current work is to understand the critical interactions between material microstructure, mechanical properties and process quality in the development of high performance aluminum alloys. The mechanical properties were investigated and correlated with microstructural features such as porosity, Fe-rich particles, secondary dendrite arm spacing (SDAS) and Si-particle length. The correlation with process quality measures such as bifilm index, density index and sludge factor (SF) were also investigated. The Si-particle lengths were found to explain variation in material strength and ductility which factors such as the bifilm index and porosity could not.

In this paper, the morphologic evolution of α-phases and their influence on mechanical properties during the hot working process of the Ti-6Al-4V alloy has been quantitatively investigated. Samples with a variety of different features of α-phase were obtained by hot working. A quantitative analysis of SEM/OM images is carried out to determine the features of α-phase before and after deformation, including the length, thickness, aspect ratio and volume fraction of α-phase. It was found that the α-phase platelet thickness increases with the increasing of forging height reduction on subsequent solution and aging treatment, larger height reduction would reduce the aspect ratio and length of α-phase and further makes the α-phase closest to equiaxed morphology. Moreover, the influence of the α-phase features on the mechanical properties was systematically investigated. The results indicate that the mechanical properties are strongly determined by the features of the α-phase, especially the thickness and volume fraction of the α-phase. This work will optimize the mechanical property by means of microstructural control and deepen the understanding of influence of α-phase features on the mechanical properties.

Bacteria can attach to stainless steel surfaces, resulting in the colonization of the surface known as biofilms. The release of bacteria from biofilms can cause contamination of food such as dairy products in manufacturing plants. This study aimed to modify stainless steel surfaces with silver nanofilms and to examine the antibacterial effectiveness of the modified surface. Ion implantation was applied to produce silver nanofilms on stainless steel surfaces. 35 keV Ag ions were implanted with various fluences of 1 × 10¹⁵ to 1 × 10¹⁷ ions•cm^-2 at room temperature. Representative atomic force microscopy characterizations of the modified stainless steel are presented. Rutherford backscattering spectrometry spectra revealed the implanted atoms were located in the near-surface region. Both unmodified and modified stainless steel coupons were then exposed to two types of bacteria, Pseudomonas fluorescens and Streptococcus thermophilus, to determine the effect of the surface modification on bacterial attachment and biofilm development. The silver modified coupon surface fluoresced red over most of the surface area implying that most bacteria on coupon surface were dead. This study indicates that the silver nanofilm fabricated by the ion implantation method is a promising way of reducing the attachment of bacteria and delay biofilm formation.

This work presents a comparative study of a series of Fe–Mn–Si alloys proposed as degradable biomaterials for medical applications. Five Fe-28wt.%Mn-xSi (where x = 0 to 8 wt.%) alloys were fabricated by an arc-melting method. All the as-cast alloys were subsequently subjected to homogenization treatment and hot forging. The microstructure and phase constituents were investigated. It is found that the grain size of the as-forged alloys ranged approximately from 30 to 50 μm. The as-forged Fe–Mn–Si alloys containing Si from 2 to 6 wt.% was comprised of duplex martensitic ε and austenitic γ phases; however, the Si-free and 8 wt.% Si alloys only consisted of a single γ phase. After 30 days of static immersion test in a simulated body fluid (SBF) medium, it is found that pitting and general corrosion occur on the sample surfaces. Potentiodynamic analysis reveals that the degradation rate of the Fe–Mn–Si alloys increased gradually with Si content up to 6 wt.%, beyond which the degradation slows down.

Al–Si–Cu alloys were cast with the unique gradient solidification technique to produce alloys with two cooling rates corresponding to secondary dendrite arm spacing (SDAS) of ~9 and ~27 μm covering the microstructural fineness of common die cast components. The microstructure was studied with optical microscopy and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and electron backscattered diffraction (EBSD). The alloy with higher cooling rate, lower SDAS, has a more homogeneous microstructure with well distributed network of eutectic and intermetallic phases. The results indicate the presence of Al–Fe–Si phases, Al–Cu phases and eutectic Si particles but their type, distribution and amount varies in the two alloys with different SDAS. EBSD analysis was also performed to study the crystallographic orientation relationships in the microstructure. One of the major highlights of this study is the understanding of the eutectic formation mechanism achieved by studying the orientation relationships of the aluminum in the eutectic to the surrounding primary aluminum dendrites.

Continuous high-temperature resistant SiC(Al) fibers were prepared by polymer-derived method using polyaluminocarbosilane (PACS) as the precursor. The formation and evolution of defects formed in the preparation of continuous high-temperature resistant SiC(Al) fibers were investigated by analyzing continuous PACS green fibers, cured products, pyrolysis process and continuous SiC(Al) fibers. The results showed that there were two major types of defects in the continuous PACS green fibers: pits and inclusion. These defects were difficult to be eliminated during the next processes. Other new defects may form during the preparation process under improper conditions, especially during the pyrolysis and sintering processes. The properties of the fibers are greatly affected by the defects. The formation of defects could be reduced to prepare high performance SiC(Al) fibers if effective measures are taken according to the formation mechanism of defects.

The precipitation process discussed in the present study involves the addition of alkaline solutions to an acidic calcium phosphate suspension. Several parameters (pH, pH buffer reagent, ageing and stirring) were investigated. The synthesized powders were calcined at 1000°C for 1 h in air, in order to study the thermal stability and crystalline phase compositions. X-ray diffraction (XRD) and ESEM analysis were used for sample characterization. It is found that all these processing parameters affect the crystalline phases evolved and resultant microstructures. Phase evolution occurred at an elevated pH level. The pH buffer reagent would affect both the phase composition and microstructure. Ageing was essential for the phase maturation. Stirring accelerated the reaction process by providing a homogeneous medium for precipitation.

The interface between natural fibers and thermoplastic matrices is studied, in which fiber-matrix wetting analysis and interfacial adhesion are investigated to obtain a systematic understanding of the interface. In wetting analysis, the surface energies of the fibers and the matrices are estimated using their contact angles in test liquids. Work of adhesion is calculated for each composite system. For the interface tests, transverse three point bending tests (3PBT) on unidirectional (UD) composites are performed to measure interfacial strength. X-ray photoelectron spectroscopy (XPS) characterization on the fibers is also carried out to obtain more information about the surface chemistry of the fibers. UD composites are examined to explore the correlation between the fiber-matrix interface and the final properties of the composites. The results suggest that the higher interfacial adhesion of the treated fiber composites compared to untreated fiber composites can be attributed to higher fiber-matrix physico–chemical interaction corresponding with the work of adhesion.

Low-cost carbon fibers (CFs) are fabricated from jute fibers after pre-oxidation, carbonization and surface repair. This paper investigates the effects of pre-oxidation heating rate on jute fibers, and explores a repair method for surface defects of CFs in C/C composite. The results show the reaction mechanism of jute fibers in air is not changed at higher pre-oxidation heating rates while a low heating rate is still required as the oxidation of jute fibers cannot be fully achieved under rapid heating. The tensile strength of CFs increases after repair with a 5% phenolic resin solution. Jute-based CFs play a positive role in C/C composite performance through crack bridging and deflection.

The cold-rolled pure copper sheets were annealed with and without a high magnetic field of 12 T. The results showed that the magnetic annealing could promote the formation of the initial recrystallized cube texture. The magnetic annealing did not dramatically change the final annealing textures, but the intensity of the recrystallized cube texture is obviously different. The differences of the recrystallized cube orientation intensity between the specimens with and without the field annealing may be attributed to the effects of the magnetic field on the mobility of grain boundaries.

Copper (Cu) is widely used as electrical conducting and contacting material. However, Cu is soft and does not have good mechanical properties. In order to improve the hardness and wear resistance of Cu, sol-enhanced Cu–Al₂O₃ nanocomposite coatings were electroplated by adding a transparent Al oxide (Al₂O₃) sol into the traditional electroplating Cu solution. It was found that the microstructure and mechanical properties of the nanocomposite coatings were largely influenced by the Al₂O₃ sol concentration. The results show that the Al₂O₃ nanoparticle reinforced the composite coatings, resulting in significantly improved hardness and wear resistance in comparison with the pure Cu coatings. The coating prepared at the sol concentration of 3.93 mol/L had the best microhardness and wear resistance. The microhardness has been improved by ~20% from 145.5 HV (Vickers hardness number) of pure Cu coating to 173.3 HV of Cu–Al₂O₃ composite coatings. The wear resistance was also improved by ~84%, with the wear volume loss dropped from 3.2 × 10^-3 mm³ of Cu coating to 0.52 × 10^-3 mm³ of composite coatings. Adding excessive sol to the electrolyte deteriorated the properties.

The duplex Nickel–Boron–Titania/Nickel (Ni–B–TiO₂/Ni) coatings were deposited on mild steel by using two baths with Ni as the inner layer. TiO₂ nanoparticles were incorporated into the Ni–B coatings as the outer layer by using solid particle mixing method. The microstructure, morphology and corrosion resistance of the duplex Ni–B–TiO₂/Ni nanocomposite coatings were systemically investigated. The results show that the duplex interface was uniform and the adhesion between two layers was very good. The microhardness of duplex Ni–B–TiO₂/Ni coating was much higher than the Ni coating due to the outer layer of Ni–B–TiO₂ coating. The corrosion resistance of the duplex Ni–B–TiO₂/Ni coating was also significantly improved comparing with single Ni–B coating. The Ni–B–10 g/L TiO₂/Ni coating was found to have the best corrosion resistance among these duplex coatings. This type of duplex Ni–B–TiO₂/Ni coating, with high hardness and good corrosion resistance properties, should be able to find broad applications under adverse environmental conditions.

7003-T5 Aluminum (Al) alloy plates with a thickness of 5 mm are welded by gas metal arc welding (GMAW) method in this work. In order to investigate the influence of stress concentration introduced by weld reinforcement on fatigue strength, the stress concentration factor of the butt joint is calculated. Microscopic and X-ray techniques were utilized to make sure there are no weld defects with large size in butt weld, which can induce extra stress concentration. The cyclic stress – number of cycles to failure (S–N) curves of the joints with and without the welder were obtained by fatigue testing, and the results show that the fatigue strength of 7003-T5 Al alloy butt joints with the weld reinforcement is 50 MPa, which is only 45% of the joints without the weld reinforcement. Fracture surface observation indicated that the fatigue source and propagation are dissimilar for the specimens with and without the welder due to the stress concentration at the weld root. The stress concentration with a factor of 1.7 has great effect on the fatigue strength, but little influence on the tensile strength.

In this research, Cu-9Pb high leaded bronze were prepared by spray forming. The microstructure and wear properties of this bronze alloy were systematically investigated. The results show that although the hardness of spray formed alloy was not increased comparing with the cast alloy, it still presented a lower wear rate and a lower friction coefficient in dry sliding wear tests as shallower grooves and more lubricating films were observed in the spray formed bronze (BSF14). Spray forming also refined the lead phase microstructure of Cu-9Pb bronze and improved its wear properties.

Corrosion behavior of 7N01 Al alloy is sensitive to chemical composition. In this paper, stress corrosion cracking (SCC) and electrochemical behaviors of A7N01S-T5 Al alloys with three different chemical compositions were investigated. The corrosion weight loss and corrosion pits depth statistics showed that Alloy #3 (4.53wt.%Zn, 1.27%Mg, < 0.001%Cu, 0.24%Cr, 0.15%Zr) possesses the best anti-SCC property, while Alloy #1 (4.54%Zn, 1.09%Mg, 0.102%Cu, 0.25%Cr, 0.15%Zr) was the weakest one. The different SCC susceptibility was mainly related to the Cu content as Alloy #3 contains higher Cu than Alloys #1 and #2. Electrochemical test result showed that Alloy #3 has higher corrosion potential and lower corrosion current density than Alloys #1 and #2. It is believed that a trace Cu can significantly improve the SC resistance of Al alloy, mainly because that Cu element can reduce the potential difference between grain inside and grain boundaries.

Microwave (MW) dielectric ceramics in (1 - x)(Li_1/2Nd_1/2)TiO₃–xCaTiO₃ (0.2 ≤ x ≤ 0.8) composition were prepared through the conventional solid-state reaction. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) indicated that the matrix phase was a continuous solid solution with orthorhombic perovskite structure. A minor amount of secondary phase was detected only in the composition of x = 0.7 and 0.8. The (1 - x)(Li_1/2Nd_1/2)TiO₃–xCaTiO₃ ceramics showed a very high permittivity of 118–153 and reasonable Q × f₀ values of 2360–5930 GHz as x increased from 0.2 to 0.8. The temperature coefficient of resonant frequency (τ_f) of the samples increased with increasing x value and was approximately linearly proportional to ε_r. Bi₄B₂O₉ addition effectively tailored the τ_f of (1 - x)(Li_1/2Nd_1/2)TiO₃–xCaTiO₃ ceramics to near zero at low temperature, and induced no degradation of Q × f₀ value. The x = 0.3 composition with 20 wt.%Bi₄B₂O₉ addition sintered at 1050°C exhibited dielectric properties of ε_r = 112.4, Q × f₀ = 2414 GHz and τ_f = 8.9 ppm/°C.

The purpose of the study is to characterize and improve the fundamental understanding of the effects of Ethyl Cellulose (EC) binder on the rheological properties of silver pastes for screen printing front electrode films of solar cells. Dispersions of silver particles (surface modified with oleic acid) in EC polymer solutions with and without thixotropic agent were prepared; and yield stress values were measured by setting shear stress to characterize the strength of interaction in pastes. Week flocculation network of silver particles is produced due to depletion of flocculation. EC polymer also has a significant interaction with thixotropic agent. Down-sweep flow curves of dispersions without thixotropic agent were measured and well fitted by Generalized Casson model. The model parameters p indicated that EC polymer with high molecular weight has a stronger shear-thinning ability. Steady-state flow, three interval thixotropy shear test (3ITT) and oscillatory measurements were conducted to study the effect of EC content on viscosity, structure rebuilding and viscoelastic properties of electrode pastes. Increasing EC polymer is not the best way to prevent the layer printed from laying down.

This work studies the photocatalytic activity of zinc oxide (ZnO) nanopowder to recover silver (Ag) metal from low Ag⁺ concentrated solution under artificial ultraviolet (UV) light. Benchmark titanium dioxide (P25 TiO₂) was used for comparison purpose. Experimental results indicated that ZnO exhibited superior performance for Ag recovery compared to TiO₂. Under optimal catalyst loading, the achieved Ag removal efficiencies were 100% and 99.94% at 0.2 g/L ZnO (1 h) and 2 g/L TiO₂ (2 h), respectively. An induction period at low concentration of TiO₂ (0.1 g/L) was observed and a mechanism was proposed. The photodissolution of ZnO was assessed and proved to be negligible. Recovered pure Ag metal was characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM), showing a promising effective Ag recovery technology using ZnO photocatalyst.

Rare earth has been widely used in materials manufacturing to improve hardness and toughness. In this paper, conventional, nano-modified and CeO₂ modified WC-12Co coatings are produced by using high speed oxygen flaming (HVOF) spraying technology. Long-term immersion and electrochemical tests of these coatings in 3.5 wt.% NaCl solution are conducted. The surface morphologies were observed to investigate the corrosion mechanisms. The results show CeO₂ modified WC-12Co coatings to possess the best corrosion resistance but the nano-modified WC-12Co coating has the worst performance. Results suggest that the improvement of corrosion resistance for CeO₂ modified WC-12Co coating can be attributed to the enhancement of interfacial strength between Co binder phase and WC particles.

A binary solvent with large density was used as dispersant for silica spheres, in which silica spheres with large diameter can suspend steadily and disperse very well. With this suspension, fine opals with 2100 nm SiO₂ mono-disperse spheres were successfully prepared by solvent evaporation method. Low pressure vapor deposition method was then used to fill the voids of the silica opals with Si, and silicon inverse opal with photonic band gaps in mid infrared region was obtained. The infrared radiation characteristic of resulted sample was examined. It is shown that silicon inverse opal structure is effective in suppressing silicon thermal radiation in the photonic band gap spectral region.

Carbon Fiber Reinforced Plastic (CFRP) composite laminates are widely used in aerospace and aircraft structural components due to their superior properties. However, they are regarded as difficult-to-cut materials because of bad surface quality and low productivity. Drilling is the most common hole making process for CFRP composite laminates and drilling induced delamination damage usually occurs severely at the exit side of drilling holes, which strongly deteriorate holes quality. In this work, the candle stick drill and multi-facet drill are employed to evaluate the machinability of drilling T700/LT-03A CFRP composite laminates in terms of thrust force, delamination, holes diameter and holes surface roughness. S/N ratio is used to characterize the thrust force while an ellipse-shaped delamination model is established to quantitatively analyze the delamination. The best combination of drilling parameters are determined by full consideration of S/N ratios of thrust force and the delamination. The results indicate that candle stick drill will induce the unexpected ellipse-shaped delamination even at its best drilling parameters of spindle speed of 10,000 rpm and feed rate of 0.004 mm/tooth. However, the multi-facet drill cutting at the relative lower feed rate of 0.004 mm/tooth and lower spindle speed of 6000 rpm can effectively prevent the delamination. Comprehensively, holes quality obtained by multi-facet drill is much more superior to those obtained by candle stick drill.

In order to analyze the effects of cold rolling parameters such as the crossing angle and axial shifting value of work rolls on the strip profile, extensive tests were carried out on a 4-high rolling mill equipped with a work roll crossing and shifting system. The results show that the strip profile is nearly flat under asymmetrical rolling. The rolling force was also analyzed in detail by changing the crossing angle and axial shifting value of work rolls.

Weld-based rapid prototyping (RP) has shown great promises for fabricating 3D complex parts. During the layered deposition of forming metallic parts with robotic gas metal arc welding, the geometry of a single weld bead has an important influence on surface finish quality, layer thickness and dimensional accuracy of the deposited layer. In order to obtain accurate, predictable and controllable bead geometry, it is essential to understand the relationships between the process variables with the bead geometry (bead width, bead height and ratio of bead width to bead height). This paper highlights an experimental study carried out to develop mathematical models to predict deposited bead geometry through the quadratic general rotary unitized design. The adequacy and significance of the models were verified via the analysis of variance. Complicated cause–effect relationships between the process parameters and the bead geometry were revealed. Results show that the developed models can be applied to predict the desired bead geometry with great accuracy in layered deposition with accordance to the slicing process of RP.

In this paper, ultrasonic gas atomization (USGA) of Zn–Al under near-zero aspiration pressure was discussed. The protrusion length of delivery tube was modified to adjust the aspiration pressure. Under near-zero aspiration pressure, melt filming was observed by camera and more fine powders were produced. While under larger subambient aspiration pressure, melt filming was unavailable, corresponding to less fine powders. The results suggest that the position of the wake near the delivery tube can be optimized under near-zero aspiration. Less protrusion of delivery tube reduces the energy loss in gas flow deflection. Both facilitate to produce finer powders.