TRANSFORMATION HYSTERESIS AND STABILITY OF STRAIN MARTENSITE IN A Ni_(47)Ti_(44)Nb_9 ALLOY

The transformation hysteresis and stability of strain martensite in Ni_(47)Ti_(44)Nb_(?) alloy havebeen studied by means of tensile tests at various temperatures and electrical resistancemeasurements as well as TEM observations.It was shown that there is a characteristicdeformation temperature and a strain range,in which the critical yield stress for stress-in-duced transformation acquires optimum matching with the yield strength of the β-Nb parti-cles.In this case,deformatian can effectively increase the transformation hysteresis,while thestrain recovery ratio remains usefully high.The martensite with irreguldar fine.twinsubstructure and martensite containing some dislocations as well as martensite intersected bythe β-Nb particles possess high stability.