材料期刊网

The transformation behavior of Ti-49.6Ni shape memory alloy was investigated under fully reversed stress/strain cycling using electrical resistance measurement. The results showed, that there was no R-transformation in the original alloy and that R-transformation occurred after stress/strain cycling. The R-phase was induced by a rhombohedral distortion of the austenite in the transition process from the high-temperature phase, also called parent phase, to the low-temperature phase, the martensite, and was characterized well by the sharp increase of the electrical resistivity. The austenite start- and finish-transformation temperatures A(s) and A(f) could be observed clearly in the original alloy, whereas they appeared less clearly after stress/strain cycling. Under plastic strain-amplitude controlled cycling with Deltaepsilon(p) = 0.05%, the transformation temperature M-s remained stable between 10(3) to 10(4) cycles. Finally we assumed that low plastic strain-amplitude controlled cycling itself, which could not do any damage to the material, might be used as a better kind of mechanical training method in comparison with the thermo-mechanical training for a stabilization of the transformation temperatures for Ti-49.6Ni shape memory alloy.