Ternary β and γ phases in the Al-Au-Cu system at 750 °C

There are many aspects of the phases and phase boundaries of the Al-Au-Cu ternary system that are still unknown. Although a 500 °C isothermal section and an 18 karat pseudobinary have been reported, many of the other constitutive relationships within the ternary are uncertain. Another unresolved issue is the range of compositions that can possibly serve as shape-memory alloys. Here we investigate the constitutive relationships in this system at 750 °C. We confirm that the γ and β phases extend deep into the ternary but that the other known compounds are largely confined to the binary edges. The suitability of β-phase compositions of lower Au content for shape memory service is established.