Effects of Au/Cu ratio and gallium content on the low-temperature age-hardening in Au-Cu-Ga alloys

The effects of Au/Cu ratio and gallium content on the low-temperature age-hardening were examined in Au-Cu binary and Au-Cu-Ga ternary alloys by hardness testing, X-ray diffraction and differential thermal analysis. In alloys in which the Au/Cu ratios greatly deviated from the equiatomic one, age-hardenability at 37 °C significantly decreased. Gallium addition lowered the liquidus temperature and increased the age-hardening rate. It is considered that the diffusion rate of the constituents increased with lowering of the liquidus temperature, and that consequently, gallium addition improved the age-hardenability.