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Abstract This study was conducted to obtain a type of aluminum matrix composites exhibiting a good strength and certain ductility at high temperature. The 25 vol% TiO 2 -75 vol%2024 Al systems were selected to fabricate the (Al 3 Ti+Al 2 O 3)/2024 Al composites with residual ∼32 vol% Al matrix through powder metallurgy. The (Al 3 Ti+Al 2 O 3)/2024 Al exhibits a good strength and certain ductility at high temperature as in the design. The microstructure of (Al 3 Ti+Al 2 O 3)/2024 Al composites was investigated. It was discovered that the in-situ Al 3 Ti reinforcement was in coarse block-shaped particles of approximately 6.9 μm in size and the Al-Al 3 Ti interface was clean. The Al 2 O 3 particles were in the nano-scale and distributed in the Al matrix in a cluster form. The high temperature compression testing of the composites was conducted at the temperatures of 573 K, 623 K, 673 K, 723 K and 773 K with the strain rate of 10−3 ∼ 0.42 s−1. The results demonstrated that the composites exhibited higher strength at the same high temperature than the other Al matrix composites with a similar volume fraction. The massive Al 3 Ti and Al 2 O 3 phases played a load bearing role at high temperatures. The residual ∼32 vol% Al matrix led the composites to acquire certain ductility. Graphical abstract Image 1 Highlights • In-situ (Al 2 O 3 +nano-Al 2 O 3)/2024 Al composites were produced by TiO 2 and 2024 Al. • The composites exhibited high strength properties between 573 K-773 K. • The composites exhibited a certain ductility for residual ∼32 vol% Al matrix. [ABSTRACT FROM AUTHOR]

The cubic Ca/Ta-substituted Li 6.55 (La 2.95 Ca 0.05 )(Zr 1.5 Ta 0.5 )O 12 (LLCZTO) electrolytes were synthesized at 800 °C with Li 3 BO 3 as additives. The optimal amount of Li 3 BO 3 and its influences on the microstructure, crystal structures, Li + conductivity and the stability of the Li 6.55 (La 2.95 Ca 0.05 )(Zr 1.5 Ta 0.5 )O 12 were studied by SEM, XRD and EIS. Among all the samples, when the molar ratio of Li 3 BO 3 to the Li 6.55 (La 2.95 Ca 0.05 )(Zr 1.5 Ta 0.5 )O 12 is 4:5, the highest Li + conductivity of 1.33 × 10 −4 S cm −1 at 30 °C is obtained. When the LLCZTO samples are exposed in air, the Li + conductivity is deteriorated possibly owing to the side reactions between the LLCZTO and the H 2 O or CO 2 in the air. The Li 3 BO 3 addition can alleviate such deterioration of the Li + conductivity. [ABSTRACT FROM AUTHOR]

Short fatigue crack propagation (SFCP) behaviour of a powder metallurgy (PM) superalloy (i.e. FGH4098) for aeroengine turbine disc application was investigated at room temperature and 650 °C in vacuum (10−3 pa) by in-situ fatigue test. The SFCP mechanism was analyzed by the microstructural characterization and assessment of the SFCP rate. The results show that the SFCP resistance of fine grained (FG) FGH4098 is slightly better than that of coarse grained (CG) FGH4098 at room temperature due to the hindering effects of grain boundary, and close to that of CG FGH4098 at 650 °C. The temperature exerts more evident influence on SFCP behaviour of FG FGH4098 due to the grain boundary oxidation compared with that of CG FGH4098. In the scenario which grain boundary oxidation is absent or insignificant, SFCP shows transgranular feature and is closely related to slip bands linked to the slip systems with high Schmid factor and/or geometric compatibility factor. Grain boundary oxidation still occurs in both FG and CG FGH4098 alloy and mainly forms Cr oxides at 650 °C, which results in intergranular or mixed-inter-transgranular SFCP and promotes SFCP to some extent for FG FGH4098 alloy. [ABSTRACT FROM AUTHOR]

Detailed transmission electron microscopy analysis on a severely deformed Al-Si composite material has revealed that partial dislocation slips and deformation twinning are the major plastic deformation carriers in ultrafine silicon grains. This resembles the deformation twinning activities and mechanisms observed in nano-crystalline face-centred-cubic metallic materials. While deformation twinning and amorphisation in Si were thought unlikely to co-exist, it is observed for the first time that excessive twinning and partial dislocation interactions can lead to localised solid state amorphisation inside ultrafine silicon grains. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides an in-depth investigation into the effects of environmental temperature and sliding speed on the tribological behaviour of a bulk metallic glass (BMG), Ti40Zr25Ni3Cu12Be20. The sliding was between the BMG and EN26 steel. The results showed that the wear resistance of the BMG increases with environmental temperature when it is below the material's glass transition temperature (T g); and that the steady friction coefficient does not vary notably. The stress on the contacting asperities influences the wear rate. Wear debris also play an important role at elevated temperatures, which could even change the wear mechanism from 2-body abrasion to 3-body abrasion under certain environmental temperature. The BMG remains amorphous, even at an environmental temperature close to its T g, indicating that frictional heating controls the microstructure transformation during contact sliding. Under a high environment temperature, a dissimilar material layer could emerge at the sliding interface, leading to a significant reduction in wear rate. [Copyright &y& Elsevier]

Abstract: We reported the formation of nanocrystalline structure in the surface layer of a pure tantalum plate under sliding friction treatment. Nanocrystalline grains of 7nm with amorphous boundaries were formed in the topmost surface layer of Ta plate. Deformation twins were also observed in the nanocrystalline grains with size below 20nm. Deformation twinning and localized amorphization are the possible deformation mechanisms in the top surface layer of tantalum induced by sliding friction. [Copyright &y& Elsevier]

Abstract: The elastic properties of a carbon nanotube (CNT) reinforced composite are affected by many factors such as the CNT–matrix interphase. As such, mechanical analysis without sufficient consideration of these factors can give rise to incorrect predictions. Using single-walled carbon nanotube (SWCNT) reinforced Polyvinylchloride (PVC) as an example, this paper presents a new technique to characterize interphase regions. The representative volume element (RVE) of the SWCNT–PVC system is modeled as an assemblage of three phases, the equivalent solid fiber (ESF) mimicking the SWCNT under the van der Waals (vdW) forces, the dense interphase PVC of appropriate thickness and density, and the bulk PVC matrix. Two methods are proposed to extract the elastic properties of the ESF from the atomistic RVE and the CNT-cluster. Using atomistic simulations, the thickness and the average density of interphase matrix are determined and the elastic properties of amorphous interphase matrix are characterized as a function of density. The method is examined in a continuum-based three-phase model developed with the aid of molecular mechanics (MM) and the finite element (FE) method. The predictions of the continuum-based model show a good agreement with the atomistic results verifies that the interphase properties of amorphous matrix in CNT-composites could be approximated as a function of density. The results show that ignoring either the vdW interaction region or the interphase matrix layer can bring about misleading results, and that the effect of internal walls of multi-walled carbon nanotubes (MWCNTs) on the density and thickness of the dense interphase is negligible. [Copyright &y& Elsevier]

Abstract: This paper aims to reveal the material removal mechanisms and the mechanics behind the vibration-assisted cutting (VAC) of unidirectional fibre reinforced polymer (FRP) composites. Through a comprehensive analysis by integrating the core factors of the VAC, including fibre orientation and deformation, fibre–matrix interface, tool–fibre contact and tool–workpiece contact, a reliable mechanics model was successfully developed for predicting the cutting forces of the process. Relevant experiments conducted showed that the model has captured the mechanics and the major deformation mechanisms in cutting FRP composites, and that the application of ultrasonic vibration in either the cutting or normal direction can significantly decrease cutting forces, minimise fibre deformation, facilitate favourable fibre fracture at the cutting interface, and largely improve the quality of a machined surface. When the vibrations are applied to both the cutting and normal directions, the elliptic vibration trajectory of the tool tip can bring about an optimal cutting process. There exists a critical depth of cut, beyond which the fibre–matrix debonding depth is no longer influenced by the vibration applied on the tool tip. [Copyright &y& Elsevier]

Highlights: [•] A relation for collapse pressure as a function of SWCNT diameter was determined. [•] All five elastic properties of SWCNT clusters in zero pressure were calculated. [•] The impact of hydrostatic pressure on the elastic properties was considered. [Copyright &y& Elsevier]

Abstract: Al–12Si components were manufactured by Selective Laser Melting (SLM) using three different atmospheres: argon; nitrogen and helium. The atmosphere type did not affect the part's density or hardness and all components reached near full relative density (>97%). The mechanical properties of the components produced in Ar and N2 were superior to those in He, especially the ductility, which has been attributed to the formation of pore clusters in the microstructure. The mechanical properties in SLM-produced components are superior to those produced using conventional method. [Copyright &y& Elsevier]

Abstract: This paper develops an elliptic vibration-assisted (EVA) technique to effectively cut fibre-reinforced polymer (FRP) composites using a simple tool. A novel vibrator was invented to work at the anti-resonant frequency to realize stable and high variational velocities. A three-dimensional microstructure-based finite element model was also established to explore the material removal mechanisms in the EVA cutting. It was found that the application of vibration can significantly decrease the cutting forces and reduce the subsurface damage in a workpiece. The vibration in the cutting direction is more effective in reducing the cutting force, but that normal to the cutting direction has the advantage of chip removal. When the vibration is applied to both the directions in the EVA cutting, an optimal cutting process can be reached, providing much smaller cutting forces, a much improved surface integrity, and an extended tool life. The study concluded that the ratio of the tool-feed-rate to the maximum vibration velocity in the cutting direction, and the ratio of the cutting distance in a single tool vibration cycle to the fibre diameter are the key parameters. To maximise the advantage of the EVA cutting, it is necessary that these two parameters are below their critical values. [Copyright &y& Elsevier]

Abstract: A novel and simple in-situ solid-state reaction route is developed to synthesize a three-dimensional (3D) porous carbon fiber film-supported Li3V2(PO4)3 membrane electrode. The carbon film is obtained via the carbonization of a bioproduct rice paper (RP). The carbon film can function as both a current collector and a 3D electronic conduction network for the loaded Li3V2(PO4)3 particles. The structure and electrochemical properties of the Li3V2(PO4)3 membrane electrode are characterized. As a free-standing membrane electrode, it exhibits good rate performance at room temperature with a specific capacity of 108 and 142mAhg−1 at 10C rate in the voltage range of 3.0–4.3V and 3.0–4.8V, respectively. It also shows good cycling performance with a specific capacity of 123mAhg−1 after 500 cycles at 1C rate in the voltage range of 3.0–4.8V. [Copyright &y& Elsevier]

Abstract: This paper establishes an analytical model to predict the normal threshold load that causes the emission of partial dislocations in silicon during nanoscratching. In the modeling, the deformation mechanisms and the sequence of microstructural changes already explored by experiment and molecular dynamics will be exactly followed; that is, with increasing the normal load of nanoscratching, phase transformation first takes place, followed by partial dislocation emission from the interface between the phase transformed zone and the original crystalline silicon when the scratching load reaches its threshold. The model postulates that the emission process represents the generation of a dipole of Shockley partial dislocations. One partial dislocation of the dipole, located at the interface, is considered immobile, while the other partial dislocation moves into the bulk of the crystalline silicon. The mobile partial dislocation slips along a crystallographic plane, and a stacking fault is formed in its wake. Based on the above, the threshold normal scratching load for the emission of a partial dislocation is determined by means of the energy criterion. The influence of the indenter geometry and the location of dislocation nucleation on the threshold normal scratching load is then investigated. Compared with the deformation of silicon under nanoindentation, the present study concludes that the threshold load under scratching is always smaller, and that a sharp indenter leads to a relatively smaller threshold load. The model prediction is well verified by scratching experiments. [Copyright &y& Elsevier]

Abstract: This paper investigates the friction and wear properties of bulk metallic glass Ti40Zr25Ni3Cu12Be20 (at%) sliding against EN26 steel in a dry environment. It was found that frictional heating plays a central role in the variation of the tribological properties of the material. When the temperature rise does not cause phase transformation but introduces plasticity, the friction coefficient decreases and the wear rate increases. A further temperature rise brings about a wear mode transition from brittle to ductile wear. When the temperature is above the glass transition temperature of the material, crystal particles emerge in the deformed subsurface, and turns the wear to a brittle mode again, even though superplastic deformation of the material also takes place in conjunction with such phase transformation. As a result, friction coefficient increases and wear rate decreases. [Copyright &y& Elsevier]

Abstract: The wear of the bearing surfaces of hip joint prostheses is a key problem causing their primary failure. This paper introduces a wear prediction model with the aid of the finite element analysis. To mimic walking, the most common activity of a human body, a three-dimensional physiological loading gait cycle was considered. The wear at the bearing surface in gait cycles was calculated based on the contact stress variation from the finite element analysis and the sliding distance obtained from three-dimensional hip gait motions. The geometry of the worn surface was updated considering the average routine activities of a patient. The model was applied to three hard-on-hard prostheses, i.e., PCD (polycrystalline diamond)-on-PCD, ceramic-on-ceramic and metal-on-metal couples. It was found that due to the gait motion, the intensity and location of the maximum contact stress in the bearing components change with the gait instances. With a given geometry and gait loading, the linear and volumetric wear on the cup surface increases with the number of gait cycles. With increasing the gait cycles, the surface wear can bring about scattered contact pressure distribution. Compared to the ceramic-on-ceramic and metal-on-metal couples, the PCD-on-PCD bearing has the lowest wear progression. It was also concluded that the computational wear model presented in this paper can reasonably predict the wear evolution in hard-on-hard hip implants. [Copyright &y& Elsevier]

Abstract: Rice paper (RP) is thermally carbonized in nitrogen to prepare three-dimensionally porous carbon films, which are used for the first time as both a free-standing active anode material and a current collector of a cathode (LiFePO4 here) for lithium-ion batteries. The latter is fabricated through a one-step co-sintering of a Li–Fe–P–O precursor top layer supported on the rice paper. The rate and cycling performances of both these electrodes are found to be rather good or even better than the traditional electrodes due to the three-dimensionally porous structure of the RP-derived carbon. We also design and fabricate an RP-based full cell constructed with the above mentioned anode and cathode together with an RP membrane as the separator. Without using traditional metallic current collectors and separator membranes, such a cell exhibits reversible cycling performance. [Copyright &y& Elsevier]

Abstract: Carbon aerogel (CA)–nickel nanocomposites were synthesized by impregnating the CAs with nickel(II) acetylacetonate (Ni(acac)2) from supercritical carbon dioxide at 30MPa and 60°C followed by thermal or chemical treatment using H2 at atmospheric pressure. The CA–Ni(acac)2–CO2 adsorption isotherm was measured at the impregnation condition and found to be linear. The decomposition of Ni(acac)2 on the CA surface was investigated using thermo-gravimetry and mass-spectroscopy. Propane was found in the gaseous decomposition products. CA–Ni composites were characterized using Infrared (IR) Spectroscopy and characteristic Ni(acac)2 peaks were found to disappear after thermal or chemical treatments. X-ray diffraction (XRD) data confirmed that after H2 treatments nickel nanocrystals were present in the CA. Transmission electron microscopy (TEM) revealed the presence of nickel nanostructures dispersed homogeneously on the surface of the CA. In the samples treated with H2 at 170°C, the average Ni nanoparticle size increased from 4.9 to 12.9nm when the Ni loading increased from 3 to 6.5wt.%. The H2 treatment at 200°C resulted in Ni nanorods with diameters of 7–11nm and lengths of 25–50nm dispersed throughout the CA surface. [Copyright &y& Elsevier]

Abstract: This paper investigates the surface integrity of polycrystalline diamond composites (PCDCs) generated by an efficient abrasive-free dynamic friction polishing. The analysis includes the polishing efficiency, surface roughness, surface damage and residual stress distribution in relation to polishing conditions and microstructures on two types of thermally stable PCDCs. Raman spectroscopy revealed that transformed phases were mainly around grain boundaries, that the magnitudes of residual stresses in polished PCDCs varied across its polished surface, and that stress concentrations over 1GPa appeared in the vicinity of grain boundaries. It was found that the PCDCs with high percentages of diamond could be polished without cracking at a much large material removal rate of 0.13mg/s (0.037mm−3/s) under a high sliding speed and pressure combination of 35m/s and 5MPa, while the PCDCs with low contents of diamond were susceptible to cracking. The underlying mechanisms of sample cracking were discussed. [Copyright &y& Elsevier]

Abstract: A reliable and accurate description of the constitutive behavior of metals under the coupled effect of extremely high strain rate has become more and more important. The conventional constitutive models available, however, do not apply when the strain rate is beyond 104 s−1. This paper establishes a new constitutive model to describe the fcc crystalline plasticity at the extreme strain rate beyond which the material sensitivity to strain rate increases dramatically. The new model distinguishes the mobile dislocations from the total dislocations and incorporates the change of mobile dislocation density to count for the microstructural evolution of the material. A unified constitutive model is then proposed. An optimization method was used to obtain globally optimal parameters in the model. The flow stress predictions by the unified model show a very good agreement with experiments within the whole strain rate range from 1×10−4 s−1 to 6.4×105 s−1. The flow stress upturn phenomenon in OFHC copper was satisfactorily described. [Copyright &y& Elsevier]

Abstract: A commercial rice paper (RP) is used for the first time as a separator membrane in lithium-ion batteries. It consists of interpenetrating cellulose fibers with a diameter of about 5–40μm to form a highly porous structure. The RP is found to be electrochemically stable at a potential below 4.5V vs. Li+/Li. Several kinds of electrode materials including graphite, LiFePO4, LiCoO2 and LiMn2O4 are used to test the compatibility of the RP in Li-ion batteries and to compare with a commercial polypropylene/polyethylene/polypropylene separator membrane. The RP separator with the same thickness gives rise to a lower resistance than the commercial separator. Due to the wonderful flexibility, high porosity, low cost and excellent electrochemical performance of the RP membrane, it is promising to partially replace commercial separators in lithium-ion batteries for low power applications. [Copyright &y& Elsevier]

Abstract: This paper develops analytically a statistical model for predicting the material removal in mechanical polishing of material surfaces (MS). The model was based on the statistical theory and the abrasive–MS contact mechanisms. The pad-MS and pad-abrasive-MS interactions in polishing were characterised by contact mechanics. Two types of active abrasive particles in the polishing system were considered, i.e., Type I – the particles that can slide and rotate between the pad and MS, and Type II – those embedded in the pad without a rigid body motion. Accordingly, the material removal is considered to be the sum of the contributions from the two types of abrasive interactions. It was found that the mechanical properties and microstructure of the polishing pad and polishing conditions have a significant effect on the material removal rate, such as the porosity and elastic modulus of the pad, polishing pressure, volume concentration of abrasives, particle size, pad asperity radius and pad roughness. It was also found that different types of active particles contribute quite differently to the material removal. When the mean particle radius is small, the material removal is mainly due to the Type II particles, but when the mean particle radius becomes large, the Type I particles remove more materials. The model predictions are well aligned with experimental results available in the literature and can be used for the material removal prediction in chemo-mechanical polishing if a proper treatment of the chemical effect is introduced. [Copyright &y& Elsevier]

Abstract: This paper presents an in-depth investigation into the formation mechanisms and microstructures of adiabatic shear bands (ASBs) in hardened AISI 1045 steel induced by high speed machining (HSM). A systematic analysis, both experimentally and theoretically, shows that a low cutting speed leads to deformed ASBs, and a high cutting speed results in transformed ASBs. The formation mechanisms of the two types of ASBs are fundamentally different. A deformed ASB is simply due to severe plastic shear, but a transformed ASB involves a process of reorientation and elongation of the martensite laths in the hardened steel, and the partitioning of elongated subgrains. It was found that a dynamic rotational recrystallization is likely the origin of the equiaxed grains in the center of a transformed ASB. [Copyright &y& Elsevier]

Abstract: This paper investigates the effect of compressive strain rate on the mechanical behaviour of single crystalline silicon nanowires using molecular dynamics simulation. It was found that of the whole range of the strain rates studied, the initial deformation of a nanowire is elastic. At lower strain rates the nanowire exhibits greater elasticity, and simple constitutive equations can be developed to describe the nanoscale structure and its deformation mechanism. With the increase in strain rate, the buckling stress increases and becomes steady at medium strain rates. On applying a very high strain rate, which is equivalent to a mechanical shock, the maximum buckling stress has a sudden rise and the silicon nanowire undergoes ballistic annihilation at both ends. [Copyright &y& Elsevier]

Abstract: Inelastic deformation of metallic glass is through shear banding, characterized by significantly localized deformation and emerged expeditiously under certain stress state. This study establishes a new constitutive model addressing the physical origin of the shear banding. In the modeling, the atomic structural change and the free volume generation are embodied by the plastic shear strain and the associated dilatation. The rugged free energy landscape is adopted to naturally reflect the rate-independent flow stress and flow serrations. Based on this, the conditions for the onset of shear banding instability are established, which enables the explicit calculation of the shear band inclination angle and its extension speed. The study concludes that shear band angle is significantly influenced by the diltancy factor and pressure sensitivity, that a shear band does not increase its thickness once emanated from a deformation unit, that the spreading speed of a shear band is intersonic, and that more shear bands, which lead to higher ductility, can be induced by high strain rates or by the introduction of a second material phase. The analysis also demonstrates that the ductility of metallic glass depends on the sample geometry and/or the stress state. [Copyright &y& Elsevier]

In this paper, we present the results of using selective laser melting (SLM) to produce biomedical beta Ti–24Nb–4Zr–8Sn components, including the manufacture of a sample acetabular cup. The density of the material increases with increasing incident laser energy (i.e. decreasing laser scan speed) and reaches a near full density value of >99% without any post-processing. The mechanical properties of the as-processed material are also compared to those of conventionally processed material. [Copyright &y& Elsevier]

Abstract: This paper develops a new constitutive model for HCP metals subjected to high strain, high strain rate and high temperature based on the theory of thermally activated dislocation motion in crystal materials. The constitutive parameters of the material are determined by a new efficient method composed of a global genetic algorithm and a local penalty-function algorithm, which guarantees that the constitutive parameters are a globally optimal solution in their theoretically allowed ranges. The application of the model to Ti6Al4V alloy shows that in the high strain rate regime, the model prediction is much more accurate than those by the Johnson–Cook and Zerilli–Armstrong models. [Copyright &y& Elsevier]

Abstract: This paper uses the finite element method to analyse the generation and evolution of residual stress in silicon-on-sapphire thin film systems during cooling. The effects of material properties, thin film structures and processing conditions, on the stress distribution were explored in detail. It was found that under certain conditions, significant stress concentration and discontinuity can take place to initiate crack and/or delamination in the systems. However, these can be minimised by controlling the buffer layer thickness. [Copyright &y& Elsevier]

Abstract: This paper investigates the feasibility to achieve grinding-hardening in a plunge cylindrical grinding process. To understand the mechanisms, a temperature-dependent finite element heat transfer model incorporating a triangular moving heat source was developed to describe the temperature field, thus to predict the thickness of the grinding-hardened layer. The analysis carried out included the variation effect of depth of cut caused by the change in wheel–workpiece engagement. The model was applied on quenchable steel 1045 and the analysis was verified experimentally. It was shown that the heating cycle in plunge cylindrical grinding is the result of consecutive heating and cooling processes, varying from location to location in a workpiece. The ratio of the workpiece speed to the infeed rate plays an important role in the heat treatment cycle. [Copyright &y& Elsevier]

Abstract: A near-β Ti–5Al–5Mo–5V–2Cr–1Fe alloy was produced using the blended elemental powder metallurgy approach. The microstructural development and distributions of the alloying elements were investigated during transformation of the heterogeneous powder compacts into the final homogenous alloy product. The influence of different alloying elements and their combination on microstructural evolution and chemical homogenisation is discussed. X-ray mapping and line scans found the order of the rates at which the alloying elements diffuse into the Ti matrix. It was concluded that the addition of 1% Fe as alloying element with the fastest diffusivity in titanium has a positive influence on the characteristics of sintered alloy. [Copyright &y& Elsevier]

Abstract: This paper investigates the effects of oxidizer concentration, pH and slurry flow rate on the material removal rate (MRR) in chemo-mechanical polishing (CMP) of Si (100) wafers. The CMP was carried out in alkaline slurry using alumina and ceria particles with hydrogen peroxide. It was found that the applications of the two particle materials lead to very different results. When using the alumina particles, the MRR initially decreases with increasing the slurry pH value until pH=9. Nevertheless, the application of the ceria particles increases the MRR before the pH of the slurry reaches 10. It was concluded that in the former, the effect was due to the particle agglomeration and the contact angle decrease of the oxidizer slurry with the wafer surface; whereas in the latter it was caused by the particle agglomeration and the modification of trivalent ceria ions. The influence of the slurry flow rate and oxidizer concentration, regardless of the particle type, was found to be similar—a higher flow rate or a higher oxidizer concentration brought about a greater MRR before reaching a plateau. Many of these were interpreted by an adhesive removal mechanism on the molecular scale. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the grinding–hardening both theoretically and experimentally with a plunge surface-grinding process. Theoretically, the paper presents a temperature-dependent finite element heat transfer model, incorporating a triangular moving heat source and various cooling conditions, to investigate the phase transformation kinetics, thus to predict the thickness of a layer hardened. The temperature variation and thickness of the hardened layer were also investigated experimentally on quenchable steel 1045 using dry air and liquid nitrogen as the cooling media. The predictions were in good agreement with the experimental results. It was found that the phase transformation follows the martensitic kinetics. The application of liquid nitrogen enhances the transformation of retained austenite to martensite and results in a refinement of the martensitic structure. [ABSTRACT FROM AUTHOR]

Abstract: Pronounced grain refinement to ultrafine or nanoscale size in initially coarse-grained Co–25Fe and Co–35Fe alloys has been achieved upon conventional compression at room temperature. Both Co–Fe alloys exhibit a large plasticity of more than 140% without fracture at room temperature, which is related to a multiscale-grained microstructure resulting from deformation-induced grain refinement. The grains refine with increasing deformation during compression. The microstructure features indicate that the possible mechanism for the strain-induced grain refinement under conventional compression is a consequence of the propagation and coalescence of dislocation cell structures with strain accumulation. [ABSTRACT FROM AUTHOR]

Abstract: Cu46Zr47Al7 bulk metallic glass (BMG) alloys with different microstructure were fabricated by adjusting the casting size. For the monolithic BMG with different diameters, the measured plasticity decreased with the increase of sample size and was mainly due to the sliding of two undeveloped parts along main shear band. Excellent compression plastic strain (∼13.2%) was obtained for the marginal BMG containing in situ nanocrystals with sample size up to 3.5mm in diameter where multiple shear bands formed. It is suggested that failure of BMG samples will occur when the temperature rise in shear layer reaches a critical value. The temperature rise is closely related to the sample size and stress drop, moreover, it can be controlled through adjusting final stress drop (via sample size) and increment rate of stress drop (via microstructure), resulting in enhanced plasticity. [Copyright &y& Elsevier]

Abstract: This paper proposes a new constitutive model to describe the dynamic plasticity of FCC metals using the thermal activation mechanism of dislocation motion. In the model development, the constitutive parameters were directly linked with the characteristics of microstructures of materials. As an example of its application, the model was used to describe the behavior of OFHC copper. To determine the globally optimized parameters of the constitutive model for OFHC copper, an improved multi-variable optimization method of constrained nonlinear programming was used based on the flow stress of the material measured experimentally. A comparison with some models and experimental data in the literature shows that the new model is simple to apply and is much better in terms of its prediction accuracy. It was shown that compared with the MTS model the new constitutive equation is explicit and can be easily embedded into a computational code of material dynamics; while compared with the Zerilli–Armstrong and Johnson–Cook models the new one reflects more precisely experimental observations. It was concluded that the new model is applicable to a wide range of problems with temperature variation from 77K to 1096K, strain rates ranging from 10−3 s−1 to 104 s−1, and strain as high as 1. [Copyright &y& Elsevier]

Abstract: Mono-crystalline silicon wafers are important materials in the semiconductor industry for fabricating integrated circuits and micro-electro-mechanical systems. To ensure high surface integrity of polished wafers, the effect of pad texture and its variation on the pad performance needs to be understood. This paper studies experimentally the dependence of pad performance on its texture deterioration by investigating its correlation with polishing time, polishing pressure, and material removal rate. The study concludes that material removal rate decreases as the cylindrical cell structure of a pad is gradually deteriorated, that there is a pad life limit beyond which polishing quality can no longer be maintained, and that the workable pad life can be extended to a certain degree by applying higher polishing pressure. [Copyright &y& Elsevier]

Abstract: The preparation of carbon black (Black Pearl 2000) supported single Pd, Pt and bimetallic Pd–Pt nanoparticles utilizing the supercritical CO2 deposition method was investigated. Palladium (II) acetylacetonate (Pd(acac)2) and dimethyl (cyclooctadiene) platinum (II) (Pt(cod)me2) were utilized as metallic precursors. The adsorption isotherms of Pd(acac)2 and Pt(cod)me2 on BP2000 in scCO2 at 20MPa and 60°C were determined. A mass transfer model was found to represent the experimental data on the kinetics of adsorption of Pd(acac)2 onto BP2000 in scCO2 fairly well with a fitting error of 5.6%. In order to prepare the supported nanoparticles, chemical reduction with H2 in scCO2 was utilized. Increasing reduction temperature and metal loading caused an increase in Pd particle size. The Pd particles were irregularly distributed and the size range of the particles was 3–100nm, whereas Pt nanoparticles were homogeneously distributed with a size range of 2–6nm. Binary metal nanoparticles could also be produced by simultaneous adsorption and subsequent reduction of the precursors. It was found that addition of Pt increased the homogeneity and reduced the particle size on the support compared to single Pd nanoparticles. From the X-ray spectrometry data, it was seen that there was a heterogeneous mixture of the bimetallic nanoparticles. Pt-rich nanoparticles had diameters of around 4nm, whereas Pd-rich nanoparticles were larger with diameters of around 10nm. [Copyright &y& Elsevier]

Abstract: Carbon nanotube films were fabricated by a new deposition technique that can minimize carbon nanotube rolling/slipping when sliding against diamond. Molecular dynamics simulations were performed to understand the friction mechanisms. Results clarify the controversial arguments in the literature and conclude that the atomically smooth surface without dangling atoms and durability of the atomic lattice structure of carbon nanotubes makes them a good solid lubricant with an ultra-low coefficient of friction of around 0.01. [Copyright &y& Elsevier]

Abstract: Using the cutting of long fibre reinforced polymer and ceramic particle reinforced aluminium as the examples, this paper tends to understand some common features in the mechanics modelling of machining composites. It demonstrates that an accurate characterisation of matrix deformation, matrix–reinforcement interaction, and reinforcement deformation are key factors for the establishment of a model to reflect the principal material removal mechanisms. A precise understanding of these factors can be achieved through a logic process of mechanism exploration, model derivation and verification. [Copyright &y& Elsevier]

Abstract: This review paper discusses some basics in using continuum mechanics and molecular dynamics to characterize the deformation of single-walled carbon nanotubes (SWCNTs). It identifies that the van der Waals force between SWCNTs in a bundle distributes symmetrically and influences the bundle formation, and that to avoid misleading results from a molecular dynamics simulation, the interaction potential, thermostat scheme and simulation parameters must be carefully selected. The paper then points out that when the necessary condition proposed by Vodenitcharova and Zhang and a compatibility condition for elastic constants are satisfied, the intersect of the bending and in-plane stiffness curves in the modulus-thickness plane can determine a unique effective wall thickness of an SWCNT and hence its Young''s modulus. [Copyright &y& Elsevier]

Abstract: This paper clarifies a common misunderstanding of the phase transformation in monocrystalline silicon under nanoindentation, namely that a pop-out represents the onset of a phase transition. Through a detailed investigation into the indentation-induced deformation of monocrystalline silicon using a Berkovich indenter, it was found that a pop-out does not correspond to the onset of the transformation. The critical contact pressure for initiating phase transformation during unloading is independent of the maximum indentation load or of the unloading rate. The size of a pop-out depends on the time it takes place (earlier and later), and its location alters the proportion of the transferred phases (amorphous and crystalline phases) after complete unloading. A lower unloading rate or a higher maximum indentation load promotes the occurrence of a pop-out. [Copyright &y& Elsevier]

Abstract: Through a systematic experimental investigation into the polishing of polycrystalline diamond composites by the dynamic friction technique, this paper identified three major regimes of polishing conditions: the regime capable of a low material removal, that enabling a safe, high removal processing, and that of an unsafe but ultra-high material removal. The study concluded that a higher polishing pressure–speed combination results in a high material removal rate, but with a greater risk of workpiece cracking. At a too low-pressure–speed combination, on the other hand, material removal may not take place. Based on the systematic experimental measurements, the paper established a polishing map to characterise the polishing conditions. It was found that using the polishing parameters determined by this polishing map, a quality surface finish can be obtained efficiently in duration about 10 times shorter than that of the abrasive polishing process currently used in industry. [Copyright &y& Elsevier]

Abstract: This paper investigates the mechanical and thermal effectiveness of a new segmented grinding wheel system with controlled radial coolant supply. The applicability of the system was examined in terms of grinding forces, specific energy and ground surface integrity in plunge grinding of AISI 4140 steel. It was found that compared with a standard grinding wheel, the new system enhanced the grindability with a lower specific energy and less application of coolant. It was also found that the new grinding system could effectively maintain the sharpness of active cutting edges, evidenced by the minimisation of ploughing and rubbing deformation in ground workpieces. The cleaning capacity of the wheel was improved and chip loading on wheel surfaces was avoided. Meanwhile, the new wheel system generated better surface integrity without tensile residual stresses. [Copyright &y& Elsevier]

This investigation explores the possibility and identifies the mechanism of damage-free polishing of monocrystalline silicon without chemical additives. Using high resolution electron microscopy and contact mechanics, the study concludes that a damage-free polishing process without chemicals is feasible. All forms of damages, such as amorphous Si, dislocations and plane shifting, can be eliminated by avoiding the initiation of the β-tin phase of silicon during polishing. When using 50nm abrasives, the nominal pressure to achieve damage-free polishing is 20kPa. [Copyright &y& Elsevier]

Abstract: Machining forces, chip formation, surface integrity and shear and friction angles are important factors to understand the machinability of metal matrix composites (MMCs). However, because of the complexity of the reinforcement mechanisms of the ceramic particles, a fair assessment of the machinability of MMCs is still a difficult issue. This paper investigates experimentally the effects of reinforcement particles on the machining of MMCs. The major findings are: (1) the surface residual stresses on the machined MMC are compressive; (2) the surface roughness is controlled by feed; (3) particle pull-out influences the roughness when feed is low; (4) particles facilitate chip breaking and affect the generation of residual stresses; and (5) the shear and friction angles depend significantly on feed but are almost independent of speed. These results reveal the roles of the reinforcement particles on the machinability of MMCs and provide a useful guide for a better control of their machining processes. [Copyright &y& Elsevier]

Abstract: The corrosion behavior of Cu x Zr100−x (x =40, 50 and 60at.%) metallic glasses prepared by rapid quenching were investigated by means of electrochemical polarization measurements and immersion tests in 0.01 and 0.1mol/L HCl solutions, respectively. The influence of the alloy composition on morphological and compositional characteristics of pit regions was discussed in detail. All the investigated Cu–Zr metallic glasses are susceptible to pitting corrosion due to the adsorption of the Cl− ions. The pit morphology is strongly dependent on the Cu concentration of the alloy. A more severe corrosion on the wheel sides compared with the air sides demonstrates that the surface characteristics play an important role in influencing the corrosion resistance of the glassy alloys. [Copyright &y& Elsevier]

Abstract: This paper uses an orthotropic shell model to investigate in detail the long axial wavelength circumferential vibration of microtubules (MTs). The deformation patterns in the vibrations were explored and their phonon dispersion relations were presented for MTs with increasing radius. It was shown that with the growth of the axial wavelength, the associated frequency of MTs would finally approach a nonzero asymptotic value, rising considerably with the increase of circumferential wave number but dropping linearly with the growing radius. This study corrects the previous misunderstanding drawn by an oversimplified model, and points out that a parabolic dispersion law does not apply to the circumferential modes when the MT bending stiffness is properly considered. [Copyright &y& Elsevier]

Abstract: This paper investigates the deformation mechanisms of MMCs subjected to micro-indentation by a spherical indenter using a three-dimensional finite element modeling. It was found that deformation behavior, hardness and work hardening of MMCs were highly dependant on the location of indentation relative to particles, volume percentage of the particle, and the size ratio of indenter to particle. The hardness of an MMC varied in a complex manner depending on the restriction on the matrix flow by reinforced particles and work hardening of the matrix material. Hardness increased with the increase of volume percentage of reinforced particles and decrease of the size ratio of indenter to particle. Matrix flow due to indentation was highly non-uniform which generated an inhomogeneous strain filed in an MMC. These pose a question that the conventional definition of micro-hardness is not very appropriate for characterizing MMCs. [Copyright &y& Elsevier]

Abstract: This paper develops a new concurrent simulation technique to couple the meshfree method with the finite element method (FEM) for the analysis of crack tip fields. In the sub-domain around a crack tip, we applied a weak-form based meshfree method using the moving least squares approximation augmented with the enriched basis functions, but in the other sub-domains far away from the crack tip, we employed the finite element method. The transition from the meshfree to the finite element (FE) domains was realized by a transition (or bridge region) that can be discretized by transition particles, which are independent of both the meshfree nodes and the FE nodes. A Lagrange multiplier method was used to ensure the compatibility of displacements and their gradients in the transition region. Numerical examples showed that the present method is very accurate and stable, and has a promising potential for the analyses of more complicated cracking problems, as this numerical technique can take advantages of both the meshfree method and FEM but at the same time can overcome their shortcomings. [Copyright &y& Elsevier]

To achieve plasticity of Ti-based bulk metallic glasses (BMGs) without sacrificing their high strength, the microstructure of Ti50Cu20Ni24Sn3Si2B1 alloy was tailored to form in situ composites. The cast rods consist of micrometer-sized NiTi dendrites surrounded by a thin metallic glass network along with a fine CuTi3 phase. The rods show high strengths of ∼1900–2250MPa and plastic strains of ∼4.5–7.8%, which are superior to the monolithic Ti-based BMGs. The microstructure–property correlations and the deformation behavior are investigated. [Copyright &y& Elsevier]

Abstract: This paper investigates the mechanisms of material removal in dynamic friction polishing of polycrystalline diamond composites through the analysis of polishing-produced debris. The specimens used were PCD compacts composed of diamond and silicon carbide. In order to uncover the debris’ structure, high-resolution transmission electron microscopy (HRTEM), electron diffraction and electron energy loss spectroscopy (EELS) were used. Additionally, the density and the sp2 to sp3 ratio in the hybridized carbon materials of the debris were estimated from the EELS spectra. It was found that the debris were mainly of amorphous structure and consisted of different forms of carbon, silicon oxide/carbide, iron oxides, etc. The results show that during polishing, the diamond has transformed to non-diamond carbon, and silicon carbide to amorphous silicon carbide/oxide. [Copyright &y& Elsevier]