On the stabilisation of martensite during direct quenching and training of some CuZnAlZr springs

Different shape-memory coil springs having Zr as an intermetallic precipitate were subjected to a direct quench and a step-quench from the β field. The directly quenched springs were then trained by the stabilised stress-induced martensite training method to obtain two-way shape-memory effect (TWSME). It is found that the presence of this stabilised martensite gives a large amount of TWSME and a smaller volume fraction of martensite transforming to β phase when heating. The presence of gamma precipitates which are produced during the training procedure plays an important role in stabilising the martensite.