Composition dependence of the rubber-like behavior in ζ₂′-martensite of AuCd alloys

The effect of aging on the rubber-like behavior of martensite in a Au-50.5 at.% Cd alloy was studied, and compared with stoichiometric Au-50% at.% Cd and a Au-49.5 at.% Cd alloy. It is found that for all these alloys the critical stress for domain reversion increases with aging, and gradually saturates at long aging time, following a Chipman function. The magnitude and the rate of the aging effect are strongly dependent on composition. The magnitude decreases monotonically with increasing Cd content, but the aging rate reaches a minimum at the stoichiometric composition. These results suggest that point defects (anti-structure defects and vacancies) play a central role in the martensite aging effect, and anti-structure defects contribute much more to the magnitude of the aging effect than vacancies do.