Experimental investigation and thermodynamic modeling of the Cu–Ag–Si ternary system

Abstract

The phase equilibria of the Cu–Ag–Si system were investigated by a combination of key experiments and thermodynamic modeling. Eighteen ternary alloys were prepared to determine the isothermal sections at 500, 600, and 700 °C of the Cu–Ag–Si system by means of X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX). The solubilities of Ag in the Cu19Si6, Cu15Si4, Cu56Si11, and hcp(CuSi) phases were measured. No ternary compound was found in this isothermal sections. Based on the experimental equilibria data from the present work, thermodynamic assessment of the Cu–Ag–Si system was carried out by the CALPHAD (CALculation of PHAse Diagrams) approach. The solution phases (Cu), (Ag), (Si), and hcp(CuSi) were described using substitutional solution model and the binary phases Cu19Si6, Cu15Si4, and Cu56Si11 with the solubility of Ag were modeled by the sublattice models. A set of self-consistent thermodynamic parameters of the Cu–Ag–Si system was obtained. The isothermal sections at 500, 600, 650, and 700 °C, vertical sections at 10 and 20 at.% Ag, and liquidus projection were calculated. The reaction scheme of the Cu–Ag–Si system was constructed. The calculated results are in agreement with the experimental data from the present work and literature.