Thermodynamic Calculation And Experimental Research Of Au-Pd-Zr Ternary System

The process of material design is promoted by rapidly development of computational materials science, as one of the thermodynamic calculation of phase diagram calculation CALPHAD (CALculation of PHAse Diagram) technology, based on thermodynamic model, widely used in multi-component material systems phase diagram calculation, predicting formation phase, phase transition temperature, etc, which providing the crucial theoretical guidance of material design.Precious metal alloys are used in aviation, aerospace, military and other key materials industries, arounding the phase diagram of materials, completing the precious metal alloy basis and research system, which provide a favorable support of precious metal alloys application. In this paper, selected the representative Au-Pd alloy in the application of this subject filed, with the Zr element forming a multi-component alloy phase diagram, which laid the high-performance design of a new precious metal alloys and development of theoretical and applied foundationIn this paper, calculated the Au-Zr, Pd-Zr and Au-Pd alloy phase diagrams by CALPHAD technique, extrapolating the Au-Zr-Pd ternary alloy phase diagram and selecting the key experiments. Specifically as follows:(1) Analyzing the thermodynamic models and the free energy expression of Au-Zr, Pd-Zr and Au-Pd binary alloy phase diagrams and the calculated phase diagram and phase diagram of the standard experiments were compared, the results of comparative analysis showed: calculated phase diagram and experimental phase diagram in terms of phase composition and the phase transition temperature were matched well, which indicating the thermodynamic data and models of Au-Zr, Pd-Zr and Au-Pd three binary alloy systems are accurate and reliable.(2) Extrapolated the liquidus projection, isothermal sections at different temperatures and vertical section of Au-Pd-Zr ternary alloy by Pandat software.(3) Selecting five key experimental points: 1 # alloy (36Au-36Pd-28Zr), 2 # (34Au-34Pd-32Zr), 3 # alloy (32Au-32Pd-36Zr), 4 # alloy (30Au-30Pd-40Zr), 5 # alloy (28Au-28Pd-44Zr), analyzing detailedly the solidification process of precipitation in order to determine the organizations consistent at the room temperature and detect the possible phase in the precipitation process. The results showed that:the detected room temperature tissue organization consistent with the prediction, indicating that the thermodynamic equilibrium calculation software Pandat is accurate and reliable.(4) For XRD patterns of the five samples are at around 2θ= 30°appear a strong diffraction peak, suggesting that there may be ternary compounds, the author established the possible phase structures of ternary compounds:AuPdZr, Zr2AuPd, Zr2Au2Pd, Pd2AuZr, Zr4Pd2Au by MS software. Simulated XRD patterns compared with experimental results showed:simulation of Zr2AuPd phase and 3 # samples were matched well, which can be inferred Zr2AuPd phase may exist. The existence of AuPdZr, Zr2Au2Pd, Pd2AuZr, Zr4Pd2Au phases require the further study.