Phase equilibria in the Cu-rich portion of the Cu–Al binary system

Abstract

The phase equilibria in the Cu–Al binary system over the temperature range 500∼1000°C and the composition range 15∼60 at.% Al have been determined using diffusion couple technique, differential scanning calorimetry (DSC) and high temperature X-ray diffraction (XRD) methods. While the results from this study pertaining to the phase equilibria α/ β and ϵ 1( ϵ 2)/liquid are in agreement with those reported in previous works, significant differences have been found between the earlier results and the present work in the composition range 25∼40 at.% Al. They are: (a) In the composition range 32∼38 at.% Al only a second order reaction, γ 1 (D8 3)→ γ 0 (D8 2), is seen to occur and not a two-phase equilibrium γ 0/ γ 1 reaction as reported before (b) The β 0 phase is absent at high temperature near 1000°C and compositions near 30 at.% Al. (c) The equilibrium eutectoid γ 0→ β+ γ 1 and peritectoid γ 0+ ϵ 1→ γ 1 reactions do not occur in this system.