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In this paper, several new powder packing methods are proposed, and the COMSOL software is used to simulate the temperature distribution under different conditions. The influence of powder packing on the growth of SiC single crystal by physical vapor transport (PVT) is studied. The results show that the heat flux of the top region of the powder is increased by trapezoid graphite and graphite ring, the radial temperature gradient of the powder is reduced, which contributes to the improve the powder utilization rate. By covering the surface of the powder with a layer of porous graphite filter, the recrystallization on the surface of the powder is inhibited, the defects of carbon inclusion and thermal stress in the SiC crystal are reduced, and the growth quality and growth rate of the SiC crystal are obviously improved. The simulation results were verified by experiment, and the results agrees well with experiment. [ABSTRACT FROM AUTHOR]

Co3O4 has been considered a promising anode material because of its high theoretical capacity (890 mAh/g) and remarkable energy density. Unfortunately, it suffers from low initial coulombic efficiency, rapid capacity fading, poor electronic conductivity, large volume changes, and aggregation during the lithium ion intercalation/deintercalation process. In this work, a series of Fe2+-doped Co3O4 nanostructured materials Co3(1-x)Fe3xO4 (x = 0, 0.01, 0.02 and 0.03) were produced by a simple chemical co-precipitation method. The Fe doping led to a slight increase of the lattice parameter, which is beneficial to the rapid diffusion of Li+ ion during the lithiation/delithiation process. Meanwhile, the Fe-doped Co3O4 sample exhibited an excellent rate capability of 886.47 mAh/g at 500 mA/g, and outstanding cyclic stability (1156.91 mAh/g for 50 cycles, with the capacity retention rate of 83.53% at the current density of 100 mA/g), demonstrating improved electrochemical performance, compared with that of pure Co3O4. The good electrochemical performance profited from the formation of oxygen vacancies by Fe doping, which provided more space for Li+ diffusion and improved the electronic conductivity of the anode material. This work provides a simple way to improve the comprehensive electrochemical performance of the transitional metal oxide Co3O4 anode electrodes for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The microstructural evolution of Ti-45 at.%Al alloy during directional solidification was simulated by applying a solute diffusion controlled solidification model. The obtained results have shown that under high thermal gradients the stable primary spacing can be adjusted via branching or competitive growth. For dendritic structures formed under a high thermal gradient, the secondary dendrite arms are developed not very well in many cases due to the branching mechanism under a constrained dendritic growth condition. Furthermore, it has been observed that, with increasing pulling velocity, there exists a cell/dendrite transition region consisting of cells and dendrites, which varies with the thermal gradient in a contradicting way, i.e. increase of the thermal gradient leading to the decrease of the range of the transition region. The simulations agree reasonably well with experiment results.

The FDM numerical simulation software, ViewCast system, was employed to simulate the low pressure die casting (LPDC) of an aluminum wheel. By analyzing the mold-fi lling and solidifi cation stage of the LPDC process, the distribution of liquid fraction, temperature field and solidification pattern of castings were studied. The potential shrinkage defects were predicted to be formed at the rim/spoke junctions, which is in consistence with the X-ray detection result. The distribution pattern of the defects has also been studied. A solution towards reducing such defects has been presented. The cooling capacity of the mold was improved by installing water pipes both in the side mold and the top mold. Analysis on the shrinkage defects under forced cooling mode proved that adding the cooling system in the mold is an effective method for reduction of shrinkage defects.

Shrinkage defects can be formed easily at Critical location during low pressure die casting (LPDC) of aluminum alloy cylinder body. It has harmful effect on the products. Mold fi lling and solidifi cation process of a cylinder body was simulated by using of Z-CAST software. The casting method was improved based on the simulation results. In order to create effective feeding passage, the structure of casting was modifi ed by changing the location of strengthening ribs at the bottom, without causing any adverse effect on the part’s performance. Inserting copper billet at suitable location of the die is a valid way to create suitable solidifi cation sequence that is benefi cial to the feeding. Using these methods, the shrinkage defect was completely eliminated at the critical location.

The microstructure, precipitate type, precipitate distribution and tensile strength of a ZL205 alloy, before and after ageing treatment, have been studied by means of optical microscopy and transmission electron microscopy. The results showed that the as-cast microstructure of the alloy was made up of α-Al and eutectic phase distributed at the grain boundaries. During ageing treatment, the tensile strength increased at first and then reduced with time, and the highest ultimate tensile strength was found to be around 488.2 MPa.

NiCrAl/20%WC coatings were prepared by laser cladding on 45 steel under different technological parameters. The effects of technological parameters on the microstructure, microstructure, hardness and wear resistance were investigated. The results show that with the increase of the scanning speed, the height, width, depth and dilution rate of the cladding layer gradually decrease, the microstructure becomes smaller and smaller, the hardness gradually increases, and the wear amount decreases first and then increases, and the wear amount is the least when the scanning speed is 600 mm/min. With the increase of laser power, the height, width, depth and dilution rate of cladding layer gradually increase. The hardness gradually decreases; The wear decreases first and then increases, and the wear is the least when the laser power is 1.2 kW. [ABSTRACT FROM AUTHOR]

NiCrAl/20%WC/MoS2 composite coatings with different MoS2 additions were prepared on the surface of 45 steel by laser cladding technology. The effects of MoS2 content on the microstructure, hardness and antifriction and wear resistance of the cladding layer were mainly studied. The results show that the content of lubricating phase has a certain influence on the hardness, anti-friction and wear resistance. With the increase of MoS2 content, the microstructure is gradually refined; the hardness gradually increases; the friction coefficient first decreases and then increases, and when the MoS2 content is 5%, the friction coefficient is at least 0.55; the wear volume first decreases and then increases, and the MoS2 addition amount is 5% When the wear volume is the smallest, the wear resistance is increased by 79% compared with the 45 steel substrate. Comprehensive analysis shows that the optimum addition amount of MoS2 is 5%. [ABSTRACT FROM AUTHOR]

Alloy composition design at the atomic scale is one of the key strategies for Ni-based single crystal superalloys (Ni-SCSs). In this article, the site preference of co-alloying elements Re-M (M: Cr, Mo, W or Re) in Ni3Al system and the strengthening effects of co-alloying elements on the shear deformation resistance of Ni3Al system are investigated using the first-principles method. It is found that the atom pairs of co-alloying elements prefer Al–Al site and the site preference of alloying elements is not affected by paired atoms. And co-alloying atom pairs occupying Ni–Ni site have a strong mutual interaction, which can be responsible for the formation of Re clusters and segregation of alloying elements. The ideal shear strength (ISS) of the quaternary Ni3Al system enhanced greatly by co-alloying elements is at least higher 11.9% than that of any Ni3Al system doped with single alloying elements, which indicates there are common effect among the co-alloying elements. The result of electronic structures shows that the strong interaction between the alloy atoms and their common the first nearest neighbors (FNN) Ni atoms is the common strengthening mechanism. The present article provides valuable guidelines for improving the mechanical strength of Ni-SCSs via alloy composition design. [ABSTRACT FROM AUTHOR]

Dilution rate is one of most important factors influencing the microstructure and performance of the laser cladding layer. In order to obtain a reasonable dilution rate in the laser cladding layer of Inconel 625 alloy, the laser cladding layers with different Fe content were prepared on the surface of 20# steel by the laser cladding technique. The influence of Fe content on the microstructure and performance of Inconel 625 alloy cladding layer was investigated. The results indicate that with the increase in Fe content in the alloy, the grain size of the cladding layer becomes coarser, the grain orientation difference increases first and then decreases, and the grain boundary angle decreases first and then increases. The hardness, high temperature wear resistance, and high temperature corrosion resistance gradually decreased. It is concluded that the dilution rate of Fe in laser cladding Inconel 625 alloy should be under 5 wt.%. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of sintering temperature on microstructures and properties of AA6061 reinforced with SiC particles composites fabricated by Ultra high-pressure sintering. Results show that little agglomeration exists in AA6061 reinforced with SiC particles with the method of SiC particles coated by nano-aluminum powders. Al4C3 formed at the interface between AA6061Al and SiCp in the composite sintered above 600 °C. In the sintering temperature range of 450 ∼ 650 °C, the maximum relative density and highest hardness could reach 99.58% and 52 HRA, and the wear resistance is also the best for the AA6061 reinforced with SiC particles sintered at 600 °C. [ABSTRACT FROM AUTHOR]

The structural, electronic, mechanical, and lattice dynamical properties of binary Ti-Au intermetallic were systematically investigated by means of first-principles calculations method. By assessing the formation enthalpies and cohesive energies, all the Ti-Au intermetallic are thermodynamically stable and Ti3Au possesses the greatest stability among all the intermetallic. Afterwards, the elastic properties such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Pugh's index, were evaluated and discussed. Additionally, the lattice dynamical properties were analyzed and discussed exhaustively for these intermetallic, the results show that all the intermetallic satisfied the dynamic stability except the γ-TiAu. [ABSTRACT FROM AUTHOR]

The structure stability, mechanical properties and electronic structures of B2-FeAl intermetallics and the influence of La/Ce doping were investigated by first-principles density functional theory calculations. Several models were established. The total energies, cohesive energies, lattice constants, elastic constants, electronic density of states of Fe8Al8 and Fe8Al7X (X = La, Ce) were analyzed. The stability of alloy systems were determined according to the cohesive energy results. The calculated lattice constants of Fe8Al7X (X = La, Ce) were found to be related to the atomic radii of the alloy elements. The calculation and analysis of the elastic constants showed that ductility of B2-FeAl can be improved by the addition of La or Ce, the order of the ductility was as follows: Fe8Al7Ce > Fe8Al7La > Fe8Al8. The results of electronic structures showed that the brittleness of B2-FeAl was mainly due to the orbital hybridization of the d orbital of Fe and p orbital of Al, showing typical characteristics of a valent bond. Specifically, the mechanism for improving the ductility of B2-FeAl is that d orbital of La/Ce is mainly involved in the hybridization of B2-FeAl. [ABSTRACT FROM AUTHOR]

Ultra high-pressure sintering (UHPS) was used to prepare AA6061/SiCp composites with different contents and the effect of sintering temperatures on microstructure and mechanical properties was investigated in this study. The results showed that a uniform distribution of nano-SiC particles (N-SiCp) is obtained by the UHPS method. With the increase in N-SiCp contents, the higher hardness and better wear resistance could be inspected. The interfacial reactions and Al4C3 phase appeared above 550 °C. The relative density of composites first increased and then decreased; with the temperature raising it reached 99.58% at 600 °C. The hardness and wear property showed the same trend with the hardness reaching 52 HRA and wear rate being 1.0 × 10−6 g/m at 600 °C. Besides, the wear mechanism of the composites is mainly composed of abrasive wear and adhesive wear. [ABSTRACT FROM AUTHOR]

The SiCp/6061Al composites with volume fractions of 10%, 20%, 30% and 40% were prepared by power metallurgy method. The effects of the volume fraction of SiCp on microstructure and mechanical properties were studied by means of phase analysis, microstructure observation, hardness test, friction test, wear and tensile test. The results show that the SiC particles distribute uniformly in the matrix and the interface bonding between the matrix and the reinforcement was exceptional. With the increase of the volume fracture of SiC particles, the distribution uniformity decreases, the hardness increases, the elongation decreases, with the tensile strength and wear resistance were increasing before slowly decrease. If the volume fracture of SiC particles is 30%, the comprehensive mechanical property is best that the hardness is 97.9 HV, the tensile strength 243 MPa, the elongation is 2.9% and wear rate is 1.21 × 10–5 g/m. [ABSTRACT FROM AUTHOR]

In this paper, the 30 vol% SiCp/6061Al composites were prepared by vacuum hot pressing sintering. The effect of SiC particle size on the microstructure mechanical properties and wear behaviour of SiCp/6061Al composites was studied. From the results, it is shown that the SiC particle distribution increases firstly and then decreases with the increase of the particle sizes, the relative density, microhardness, elongation, and wear rate increase firstly and then slightly decrease. If the SiC particle size is 16 μm, the comprehensive properties of the composite are the best. [ABSTRACT FROM AUTHOR]

Graphite/6061 aluminum (G/6061Al) composites with different content of graphite were ultra-high pressure (UHP)-sintered and hot pressing (HP)-sintered, respectively. The result shows that homogeneous dispersion of graphite flakes in the 6061Al matrix can be achieved using graphite flakes coated by nano-Al particles, both in the UHP-sintered and in the HP-sintered composite. Due to the comprehensive effects of ultra-high pressure, high temperature and formation of Al4C3, the UHP-sintered composites endowed with higher relative density, higher hardness, stronger tensile strength and better wear resistance than the HP-sintered composite. The highest tensile strength of the UHP-sintered with 5 vol.% graphite is 183 MPa. Wear test reveals that the wear rate of the UHP sintered with 10 vol.% G/6061Al decreases drastically when the sintering temperature is 650 °C or higher, which is one to three orders of magnitude lower than that of the HP-sintered. The lowest wear rate of the UHP sintered with 10 vol.% graphite is 0.15 × 10−5 g/mm, while that of the HP-sintered composite is 133 × 10−5 g/mm. [ABSTRACT FROM AUTHOR]

A novel Si-Al alloy prepared by spray forming process investigated in this paper. Experimental results show that fine and homogeneous grain structure is obtained in as-deposited alloy. In addition, hot pressing process can eliminate the porosities formed at deposition process. Microstructure analysis show that the primary silicon fractured at a given stress and the particles congregated in microzone with increasing of the stress. After hot pressing, the alloy exhibits well physical and mechanical characteristics, the density is 2.514 g·cm3, the coefficient of thermal expansion is 10.3 × 10−6 K−1 at the range from room temperature to 100 °C, the thermal conductivity can reach 132 W·m−1·K−1, the ultimate compressive strength and Brinell hardness is 97.2 MPa and 130 HB, respectively. [ABSTRACT FROM AUTHOR]

Three kinds of SiCp/Al-Si-Mg composites, containing 20%, 40% and 60% volume fraction of silicon carbide particles (SiCp) were respectively sintered at high cubic anvil pressure, using SiC powders prepackaged by aluminum. Then microstructures of the composites were investigated, and the influences of pressure, sintering temperature and volume fraction of SiCp on the microstructures were analyzed. Results show that the composites own homogeneous microstructures, high density and few porosities. In the composites, SiCp and Al matrix were bounded to each other tightly and few agglomeration of SiCp or aluminum was observed. With the volume fraction of SiCp increased, the pinning effect of the reinforcement on the Al matrix is enhanced. With the sintering temperature and pressure increased, densities of the samples are also increased. Energy Dispersive Spectrometer (EDS) and X-ray diffraction (XRD) results show that there are transition layers and Al4C3 phases formed at the interface between SiCp and Al matrix when fabricated under pressure of 3.0GPa and temperature of 620 °C. [ABSTRACT FROM AUTHOR]

Flexible supercapacitors (SCs) have attracted much attention from researchers on account of their excellent safety, high power density, fast charging/discharging speed and long cycle life. Conventional hydrogel electrolytes will freeze when the operating temperature drops below zero degree, limiting the practical applications of SCs. Here, we proposed a strategy to prepare a highly conductive organohydrogel electrolyte (OHE) with excellent anti-freezing property and moisture retention by soaking poly(2-acrylamido-2-methypropane sulfonic acid)/poly (acrylamide) (PAMPS/PAAm) hydrogel into phosphoric acid/glycerol (PA/Gly) co-solvent. The OHE possessed favorable flexibility and excellent electrical conductivity of 9 and1.98 S/m at room temperature and −40 °C, respectively. Meanwhile, the prepared SCs obtained high specific capacitance, superior capacitance retention rate of 75.65% and excellent mechanical flexibility at −40 °C, compared with those at room temperature. Moreover, this work would provide a novel and promising approach for the development of flexible wearable electronic devices with low-temperature stability. • A novel phosphoric acid/glycerol co-solvent was proposed for outstanding anti-freezing organohydrogel electrolyte. • High capacity retention rate under long-cycle at −40 °C. • The SC retains excellent flexibility at −40 °C. • A simple and effective strategy is provided for energy storage devices with low-temperature stability. [ABSTRACT FROM AUTHOR]

Abstract: Ti45Zr35Ni20−x Pd x (x =0, 1, 3, 5 and 7, at%) alloys were prepared by melt-spinning. The phase structure and electrochemical hydrogen storage performances of melt-spun alloys were investigated. The melt-spun alloys were icosahedral quasicrystalline phase, and the quasi-lattice constant increased with increasing x value. The maximum discharge capacity of alloy electrodes increased from 79mAh/g (x =0) to 148mAh/g (x =7). High-rate dischargeability and cycling stability were also enhanced with the increase of Pd content. The improvement in the electrochemical hydrogen storage characteristics may be ascribed to better electrochemical activity and oxidation resistance of Pd than that of Ni. [Copyright &y& Elsevier]

Abstract: Ti45Zr35Ni13Pd7 alloys are prepared by melt spinning at different cooling rates (v). The phase structure and electrochemical hydrogen storage performance are investigated. When v is 10m/s, the alloy consists of icosahedral quasicrystalline phase (I-phase), C14 Laves phase and a little amorphous phase. When v increases to 20 or 30m/s, a mixed structure of I-phase and amorphous phase is formed. Maximum discharge capacity of alloy electrode decreases from 156mAh/g (v =10m/s) to 139mAh/g (v =30m/s) with increasing v. High-rate dischargeability at the discharge current density of 240mA/g decreases monotonically from 61.2% (v =10m/s) to 56.8% (v =30m/s). Cycling retention rate S 20 increases from 62.2% (v =10m/s) to 66.1% (v =30m/s) with increasing v, which is ascribed to the increase in amorphous phase. [Copyright &y& Elsevier]

Abstract: Ti45Zr30Ni25Y x (x =1, 3, 5 and 7) alloys were prepared by melt-spinning at wheel velocity of 20ms−1. The effect of additive Y on phase structure and electrochemical performance of melt-spun alloys was investigated. Ti45Zr30Ni25Y x melt-spun alloys were composed of I-phase and amorphous phase. The amorphous phase increased with increasing x value, indicating amorphous forming ability improved with increasing Y content. The maximum discharge capacity and high-rate dischargeability decreased with increasing x value, which may be ascribed to the decrease of nickel content. Cycling stability first increased with increasing x from 1 to 3, and then decreased when x increased to 7, which was resulted from the combined effect of the decrease of nickel content and the increase of amorphous phase. [Copyright &y& Elsevier]