Xie Ming

Virtual Crystal Approximation of Pd-Ru-Zr System

Abstract The phase stability of Zr and Ru doped Pd system has been studied using the virtual crystal approximation (VCA) in density functional theory (DFT). Three possible VCA models have been set up for Zr and Ru doped Pd system, and elastic constants and tetragonal shear constant, bulk modulus and shear modulus, Young modulus and Cauchy press, density of states in Zr and Ru doped Pd system were also analyzed. The results show that Pd-5Ru-1Zr[T(3)] is the most stable phase in Pd-Ru-Zr system according to tetragonal shear constant, and Pd-10Ru-1Zr[T(2)] is the most brittle phase and has more directional bonding according to Cauchy press. Along with replacing Pd with Ru and Zr in the solution, the structure becomes unstable both energetically and geometrically, and the increase of Ru and Zr content can improve the strength of the chemical bonding and enhance the hardness of Pd-Ru system, but reduce their phase stability.

Effects of Zn Content on the Grain Growth Law of Ag-Cu-Zn Alloys

Abstract Grain growth behaviors of Ag-Cu-Zn alloys with different contents of Zn were studied at various heat treatment temperatures and for different holding time. The experimental results show that the grain grows along with the increase of the holding time. The higher the content of Zn is, the larger the grain size will be under the same holding time. The grain growth exponent n increases and the grain growth active energy Q decreases with the increase of the content of Zn

Effect of Zr, Mo and Y Adding on Microstructure, Mechanical and Electrical Properties of Au-Pd, Pt-Ir and Pd-Ru Systems

Abstract The effect of Zr, Mo and Y adding on mechanical and electrical properties of Au-Pd, Pt-Ir and Pd-Ru systems was investigated. The alloys were prepared in a vacuum high frequency melting furnace. X-ray diffraction and metallographic microscopy were employed to detect the microstructures. Electric bridge and eddy current conductive instrument were used to test the electrical resistivity, and the mechanical properties of the alloys were tested by AG-X100KN type tensile testing machine. The results show that adding of rare metal elements in Au-Pd, Pt-Ir and Pd-Ru systems could refine structures of the alloys effectively, increase their melting points, densities and electrical resistivities, and improve mechanical properties of the alloys, but the elongations of the alloys is decreased.

First Principles Study of Stability and Thermal Properties of AuxCuy Compounds

Abstract The stability and the thermal as well as mechanical properties of AuxCuy intermetallic compounds were investigated by density functional theory (DFT). The calculated cohesive energy and the formation enthalpy of AuxCuy phases show that they are thermodynamically stable structures and the calculated lattice constants are in good agreement with those of the experiments. The heat capacities of the compounds were calculated by a quasi-harmonic approximation (QHA) method. The Debyes temperature as a function of strength of chemical binding for each compound was also discussed. The elastic properties such as bulk modulus and Youngs modulus were evaluated by Viogt-Reuss-Hill approximation. The phonon spectrum and the density of phonon states of AuCu compounds were calculated to determine the stability of two AuCu phases. The new knowledge from this study will be used for future development of Au-Cu alloy system.

Effects of Zr, Mo and Y-Doping on Microstructure and Mechanical, Electrical Properties of Au-Pd Binary Alloy

Abstract Au-Pd alloys doped with Zr, Mo and Y, respectively, were prepared in a vacuum high frequency melting furnace. The effects of rare metal doping on Microstructure and mechanical, electrical properties of the binary alloy was investigated. X-ray diffractometer and metallographic microscopy were employed to detect the microstructures. Electric bridge and eddy current conductive instrument were employed to test the electrical resistivity and the mechanical properties of alloys were tested by AG-X100KN type tensile testing machine. The results show that adding rare metal elements into Au-Pd system could refine microstructure effectively, increase the melting point, density and electrical resistivity of the alloy, and improve mechanical properties, but the processing property of the alloy is decreased.