Phase equilibria thermodynamics and solidified microstructure in the Ag-Cr-Zr system

Abstract

Ag-Cr-Zr alloy is a promising Zr-based alloy with excellent strength and hardness. Lack of investigations on phase equilibria and solidified microstructure of the Ag-Cr-Zr system limits the design of high-performance Zr-based alloys. Solidified microstructure and phase transition temperature in the Ag-Cr-Zr system are experimentally investigated using scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and differential scanning calorimetry. The microstructure of the ca-cast Ag-Cr-Zr is investigated in detail, and a liquid miscibility gap extending from Ag-Cr binary system is measured. The phase transition temperatures along three vertical sections are determined. Based on these experimental results and critical literature review, a thermodynamic modeling of the Ag-Cr and Ag-Cr-Zr systems was constructed by CALPHAD method, and the calculated phase diagram is in accordance with the experimental data. Besides, the Scheil solidification is simulated and the simulated results agree with the observed solidified microstructure. The reaction scheme for the whole Ag-Cr-Zr ternary system is calculated for the first time. This work not only fills in the gap in the thermodynamic description of the Ag-Cr-Zr system, but also provides a hybrid approach of thermodynamic calculations and key experiments for the sake of obtaining the desired solidified microstructure.