Vacancies and stabilisation in martensitic Cu-Zn-Al single crystals

The stabilisation of the 18R stress induced martensite in Cu-Zn-Al single crystals has been measured as a function of the ageing time and the previous thermal treatment in the high temperature β phase. It is found that the initial and final stages of the stabilisation present a different behavior, and only the latter is related to the quenched-in vacancy concentration. It is confirmed that the martensite does not reach its thermodynamical equilibrium state, although the vacancies remain mobile. It is suggested that the evolution of the martensite can be rationalised by the combined action of mobile vacancies and precursors of the γ equilibrium phase