Phase Relations in the Cu3Ag1-xAux, Ag3Au1-xCux and Au3Cu1-xAgx Ternary Systems

Abstract
The phase relations of Cu3Ag1-x Au x , Ag3Au1-x Cu x and Au3Cu1-x Ag x (0≤x≤1) were studied by X-ray diffractometry and differential thermal analysis. In the Cu3Ag1-x Au x and Ag3Au1-x Cu x systems, an Al-type solid solution phase α, an L12-type ordered phase α' and two kinds of two-phase region, α(Cu)+α(Ag) and α'(Cu)+α(Ag), were observed, and the phase boundaries were determined. α(Cu) means a Cu-rich phase of the Al type. On the other hand, in the Au3Cu1-x Ag x system, only an α-phase was detected over the whole composition range, except for x=0 (Au3Cu). The experimental results were interpreted by a treatment based on the Bragg-Williams approximation.