Ageing effects in a Cu-Al-Ni shape memory alloy

Ageing of a Cu-14.3Al-4.1Ni (wt.%) shape memory alloy was investigated by resistometry and scanning electron microscopy. Four stages were distinguished in isochronal annealing experiments. Underlying processes were discussed with respect to the changes observed in the particular stages. In the early stages of ageing, annealing of quenched-in vacancies is probably the dominant process; the effect of ordering processes seems to be negligible. A decrease in the hysteresis width precedes a pronounced gamma(2) phase precipitation, which takes place at temperatures above 300 degreesC. Above 370 degreesC, the alloy ability of martensitic transformation is being lost.