Applied Mechanics and Materials Vols. 278-280

Abstract: Hot forming is the advanced technology that integrates traditional heat treatment and cold stamping. The ultra high strength component with the tensile strength 1600 MPa can be manufactured by hot forming. The tensile tests of the hot forming material and part are investigated. The yield limitation of the part by hot forming is more than 1000MPa, and the strength limitation is more than 16000MPa. Three-point bending experiments of the reinforced beam by cold stamping and hot forming are carried out. The experimental results show the parts by hot forming have excellent loading capability and impact resistance. The optimization design method for hot forming part is investigated and presented.

Abstract: In this study, monodispersed Tb3+ ions were successfully dispersed in the polyacrylonitrile (PAN) solution. Tb3+/PAN composite fibers were fabricated by electrospinning the PAN solutions containing different amount of Tb3+ ions. Further investigation showed that Tb3+ ions were homogeneously dispersed in the fibers individually. The composite fibers showed a uniform and continuous morphology. The as-spun fibers were characterized by Field Emission Scanning Electron Microscope (FE-SEM) and X-ray diffraction (XRD)

Abstract: In this paper, the morphology of machined surface in turning NbC particle reinforced iron-base composites was investigated. It indicates that since the dispersive distribution of reinforcing particles, the machined surface is likely to occur various defects such as tool traces, small pits, discontinuous grooves or micro-cracks. Moreover, the surface generation mechanism was discussed. There exist three different behaviors for reinforcing particles such as brittle breakage, pressed into or flaking off the machined surface during machining. Generally, particles of small diameter are likely to be pressed into the matrix and the machining defects are relatively slight. However, particles of large diameter are likely to break or flake off, which makes surface integrity deteriorate.

Abstract: The general mathematical formulation under unidirectional solidification with mushy layer is developed. For the steady state of solidification, concentration and temperature fields in the mushy region are given as functions of a solid volume fraction. The nonlinear model of solidification in mushy zone is changed into system of the second order ordinary differential equation with free boundary conditions, which is solved using numerical calculating method. Solid volume fraction at the solid-mush interface is also obtained. For fixed control conditions, mushy layer width of Fe-Ni alloy in unidirectional solidification is predicted.

Abstract: Based on the backscattered electron (BSE) images and IMAGEJ image analysis software, the average grain size of WC in ultrafine grained WC-Co cemented carbides was measured. The result shows that BSE images of the polished surface not be etched are suitable for quantitative evaluating the grain size of WC in the ultrafine grained hardmetals. Both linear intercept method and equivalent circle diameter method can be used to accurately measure the grain sizes of WC in ultrafine grained hadmetals by using IMAGEJ software. Measurement results of WC grain sizes coincide with the conclusion of X-ray diffraction method

Abstract: When using Large-scale semi-opened copper mould die-casting machine, it can reduce the shrinkage cavity and porosity, improve the surface roughness and the mechanical properties of the copper mould. But its process parameters are selected by experience, which result in unstable quality of the anode plate copper mould. In this paper, the temperature and stress fields of the copper mould were simulated using finite element method. And the effects of the initial temperature on the copper mould quality were studied further. The preliminary optimization scheme of the die-casting initial temperature was gained, which can provide the foundation for the further process parameters optimization of the copper mould die-casting.

Abstract: Modern composite armor plate is generally composed of faceplate with high hardness and backplate with good toughness. 45 steel/60Si2CrA multilayer composite casting blank with 11 layers, containing 60Si2CrA steel as faceplate and 45 steel as backplate, was fabricated by composite casting. The deformation and heat treatment process of 45steel/60Si2CrA multilayer composite plate were studied. The results show that the interfaces between faceplate and backplate have good combination and the thickness of each layer is basic uniform by reasonable deformation distribution. Yield and tensile strength of the composite plate reaches 956MPa and 1018MPa, the hardness of 45 steel layer and 60Si2CrA layer is 448HV and 536HV respectively after the heat treatment of 860°C water quenching+ high temperature tempering. The mechanical properties meet the qualification of armor plate. The bulletproof test displays that 45 steel/60Si2CrA multilayer composite armor plate can prevent the breakthrough of DAP51B type bullet with the velocity of 500m/s.

Abstract: Electrical conductivity and tensile strength of Cu–0.22 wt.%Cr–0.05 wt.% Zr–0.05 wt.% Zn alloy were investigated after cold working and aging treatment. The results show that good combination of the physical and mechanical properties can be obtained after solid solution at 940°C for 1h and aging at 450°C for 2h. Aging precipitation phase was dealt with by transmission electronic microscope (TEM). The fine precipitation of Cr and Cu4Zr is found in copper matrix. The strength and electrical conductivity can reach 463.23MPa and 85.65% IACS, respectively.

Abstract: A novel organic nanocomposite consisting of chlorinated polyethylene (CPE), 2, 2’-methylene-bis-(4-methyl-6-cyclohexylphenol) (ZKF) and 4, 4’-thio-bis-(3-methyl-6-6tert-butyl- phenol) (BPSR) was prepared in this article. It was found that the presence of three-dimensional supra-molecular intermolecular hydrogen-bonding interactions was useful to not only compress and aggregate the molecularly dispersed ZKF and BPSR into nano-scaled particles, but also partially block the generated nanoparticles and effectively prevent them from over aggregation into large particles. The DMA results showed that there was a critical concentration for BPSR. When BPSR content was beyond the critical value, a novel loss peak was observed because of the formation of ZKF-BPSR-rich phase. These may imply that CPE/ZKF/BPSR nanocomposites possessing both high loss peak and controllable loss peak position can be more efficient in damping performance.

Abstract: In this paper, the organic hybrids materials consisting of polarized polymers and small molecules were prepared and the morphology properties were studied by SEM. For CPE/BPSR (60/40) hybrid, the BPSR crystals existed primarily as micro-sized particles, and the particles size distribution was large. The CPE/ZKF (60/40) hybrid was almost in the amorphous state and there was only a small amount of crystallites dispersed in the amorphous phase. Though the interfacial interaction between BPSR particles and CPE matrix was poor, one of the interesting phenomena was observed, when a small amount of BPSR was incorporated into CPE/ZKF hybrid. The domain size of BPSR was dramatically decreased and existed as nano-particles in the CPE/ZKF/BPSR composites. In the case of CPE/ZKF/BPSR composites, the three-dimensional hydrogen-bonding networks could compress and aggregate the molecularly dispersed BPSR into nano-scaled particles.