Age-hardening in a Gold–Nickel Alloy

Abstract

ONE factor which may limit the mechanical strength which can be achieved in a conventional age-hardening alloy is the volume fraction of the alloy which can separate out as a precipitate. This is determined by the change in solute solubility in going from room temperature to the highest possible solution treatment temperature, that is, to the solidus temperature. There is, however, a small class of alloy systems (gold–nickel, gold–platinum and chromium–tungsten) to which this limitation does not apply. In these systems complete miscibility occurs at high temperatures, but at lower temperatures there is a miscibility gap. Although precipitation phenomena occurring in these systems in alloys of high solute concentration have to some extent been studied1–5, the accompanying age-hardening effects have been almost totally neglected. The purpose of this communication is to report the results of a preliminary study of age-hardening in an equiatomic gold–nickel alloy.