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Abstract
Simultaneous measurements of acoustic emission and thermal emission have been made during the martensitic transformation of a Cu-Zn-Al alloy after quenching from temperatures Tq between 300 and HOOK. Just after the quench a strong dependence of the thermal and acoustic data on Tq has been observed. This dependence is almost suppressed when the alloy is aged (ageing time t≈50 ks) at room temperature (ageing temperature Ta≈295 K). The results show that the transformation temperature and enthalpy are sensitive to the state of the β-phase after the quench and that the transformation entropy is independent of Tq The acoustic emission is very sensitive to the excess of quenched-in free vacancies in the system. Permanent effects due to γ-type precipitates have also been detected from the energy dissipated by irreversible processes.