QUENCHED-IN DEFECTS AND MARTENSITIC-TRANSFORMATION IN CU-AL-BE SHAPE-MEMORY ALLOYS

From positron lifetime and calorimetric measurements, the concentratio n and nature of the defects introduced by quenching from different T-q temperatures, and their influence on the martensitic transformation u ndergone by a Cu-Al-Be shape memory alloy are studied. The main effect of quenches is to modify the concentration of single Vacancies in the system. The obtained dependence of the thermodynamic properties (tran sition temperatures and latent heat) of the martensitic transition upo n T-q, is explained in terms of the effective relative change of Be co ncentration due to quenched-in vacancies. Results are compared with pu blished data for other Cu-based shape memory allays. (C) 1997 Acta Met allurgica Inc.