Experimental investigation and thermodynamic modeling of the Cu–Mn–Zn system

Abstract

Abstract The phase equilibria of the Cu–Mn–Zn system at 550 °C were investigated using 4 diffusion couples and 25 equilibrated alloys. The preliminary phase relations resulting from diffusion couples were used to select the compositions of the equilibrated alloys. The samples were examined by means of X-ray diffraction, optical microscopy, scanning electron microscopy with energy dispersive X-ray spectrometry and electron probe microanalysis. The experimental results show no existence of any ternary compound at 550 °C. The phase separation of the β(CuZn)-phase (bcc_A2 structure based on approximate Cu49Zn51, in wt.%) into β and β2 was observed in the diffusion couple of Cu73Mn27 (in wt.%)/Zn and in the ternary alloy of Cu42.4Mn8.8Zn48.5 (in wt.%). There is a debate on such a phase separation in the literature. An order/disorder (A2/B2) transition was inferred to exist according to the present experimental result. All the experimental phase diagram data available from the literature were critically reviewed. A set of self-consistent thermodynamic parameters for the Gibbs energies of individual phases in the Cu–Mn–Zn system was then obtained by using the CALPHAD approach taking into account the reliable data from the literature and from the present work. Comprehensive comparisons between the calculated and measured phase diagrams showed that most of the experimental information is satisfactorily accounted for by the present thermodynamic modeling.