Martensite destabilization in Au_7Cu_5Al_4 shape-memory alloy

摘要

Aging-induced changes in the austenite peak (A_P) temperature of Au_7Cu_5Al_4 shape-memory alloy are investigated. Whereas heat treating the parent phase at temperatures >140 °C or aging the martensite for long times at room temperature both stabilized the A_P to ～80 °C, low-temperature excursions into the parent phase caused the subsequent A_P to drop to ～60 °C and the transformation hysteresis to decrease. The evidence indicates that this destabilization of the martensite is caused by time-dependent relaxation of elastic constraint due to parent-phase lath migration during the preceding low-temperature austenitizing treatment. This mechanism of aging is different from that of the better-known symmetry-conforming short-range order phenomenon.