Study On The Phase Diagram Thermodynamics And Thermal Conductivity Models Of The Cu-Cr-Zr-Ag-Y Multicomponent Systems

With the rapid development of China’s high-tech industries,Cu-based alloys as core materials are widely used in the above-mentioned high-tech industries.Elements Ag,Zr,Cr and Y are commonly used as additives for high strength and high conductivity to improve the mechanical properties of the alloy.It is of great significance to fully grasp the phase equilibrium,thermodynamic properties and thermophysical property of the Cu–Cr–Zr–Ag–Y system for the development of high-strength and high-conductivity copper alloys.In this work,the microstructure and phase equilibrium relationship of Cu–Ag–Zr,Ag–Zr–Y,and Cu–Ag–Cr–Zr alloys were studied by key experiments and CALPHAD（CALcalculation of PHASE Diagrams）method.At the same time,the CALPHAD method and thermal conductivity model were used to experimentally study and calculate the thermal conductivity of the binary systems of Cu–Ag–Cr–Zr system.This work is as follows:（1）The phase equilibria of the Cu–Ag–Zr system at 500°C and 600°C were determined by X-ray diffraction（XRD）and scanning electron microscope（SEM）with energy dispersive X-ray spectrometry（EDS）techniques.Invariant reactions involving the ternary Cu₄Ag Zr phase were investigated by differential scanning calorimetry（DSC）techniques and seven invariant reactions were determined.Two as-cast alloys were prepared to study the alloys solidification behavior.The solubilities of Cu and Ag in the binary phases were measured,and the ternary compound Cu4Ag Zr was found with compositions of Cu58.70-72.57Ag10.31-21.52Zr16.74-19.78 and Cu_58.18-75.04Ag_6.08-23.36Zr_17.50-18.88 at 500°C and 600°C,respectively.Thermodynamic assessment of the Cu–Ag–Zr system was carried out based on the available experimental data from the literature and the present work which a set of self-consistent thermodynamic parameters of the Cu–Ag–Zr system was obtained.The isothermal sections at 500°C,600°C and 750°C and liquidus projection were calculated,and the reaction scheme was constructed.The solidification behaviors of as-cast alloys were simulated under Gulliver-Scheil non-equilibrium condition.The calculated phase equilibria and simulated solidification behaviors are in agreement with the experimental data.（2）The phase equilibria at 800°C,600°C and 500°C in the Ag–Zr–Y system were investigated by means of XRD and SEM/EDS techniques.The solubilities of Zr and Y in the binany phases were measured,and no ternary compound was found in these isothermal sections.Thermodynamic parameters of the Ag–Zr–Y system were assessed based on the experimental data from the present work and the literature which a set of self-consistent thermodynamic parameters of the Ag–Zr–Y system was obtained.The isothermal sections at 800°C,750°C,600°C and 500°C and liquidus projection were calculated,and the reaction scheme of the Ag–Zr–Y system was constructed.The calculated results are in agreement with the experimental data.（3）Based on the thermodynamic parameters of Cu–Ag–Cr–Zr system obtained by literature evaluation and this work,the thermodynamic database of the system was constructed.The isothermal sections of Cu–Ag–Cr–Zr system at 600°C and 700°C at 5.0 at.%Zr were calculated by thermodynamic database.6 equilibrium alloys and 4 as-cast alloys were designed and prepared.The phase equilibria and the solubilities binary phases of Cu–Ag–Cr–Zr system at 600°C and 700°C at 5.0 at.%Zr were determined which three four-phase regions and four three-phase regions were determined and extrapolated and the experimental phase diagrams were constructed.By the same means,the microstructure and phase composition of the as-cast alloy were observed and analyzed,and the solidification process diagram of the as-cast alloy under the non-equilibrium condition was calculated.The calculated simulation results were consistent with the experimental ones.（4）The binary systems of the Cu–Ag–Cr–Zr system were calculated through the database of the one system,and 11 equilibrium alloys at 600°C isotherm were designed and prepared by alloy method.The phase equilibria and compositions of the alloys were analyzed by SEM/EDS.The thermal diffusivities of the alloys at 20°C,100°C,200°C and 300℃were measured by laser flash method,and the densities were measured by Archimedes method.The specific heats of each alloys at each temperature points were calculated by thermodynamic database,and the experimental thermal conductivities of each alloys were calculated by the equation.Based on the experimental data of the literature and the present work,the thermal conductivity parameters of pure elements Ag,Cr and Zr,the solid solution（Cu）and（Ag）phases,the linear compounds Cu₅Zr,Cu₁₀Zr₇,Cu Zr₂ phases and the two-phase regions of the Cu–X（X=Ag,Cr,Zr）systems were also optimized.The thermal conductivity of ones systems at various temperatures and compositions were calculated,and the calculated results were consistent with the experimental ones.The thermal conductivities of the Cu–Ag and Cu–Cr systems at 0-300℃versus temperatures and compositions were calculated,and the change trends of thermal conductivity were obtained.Figure[51]Table[17]Reference[184]...