POSITRON DOPPLERBROADENING MEASUREMENTS IN CU-AL-NI BASED SHAPE-MEMORY ALLOYS

Positron annihilation Dopplerbroadening measurements were carried out on Cu-Al-Ni based alloys to which Ti, and Ti and Mn was added. The mea surements reveal a drastic effect in the S-parameter behavior when the defects anneal out at the transition from martensite to the beta phas e, When crossing the transition region several times, an increase of t he S-parameter value is observed. This is interpreted as due to the fo rmation of dislocations and precipitate-martensite interfaces. In the alloy with Mn a distinct behavior is observed attributed to vacancy cl uster formation.