Criteria for pseudoelasticity in near-equiatomic NiTi shape memory alloys

It was observed that the reverse transformation of stress-induced martensite occurred at a temperature some 20 K higher than that of thermal martensite. The increase in temperature for the reverse transformation was indicative of a stabilisation effect. This stabilisation effect was attributed to the change in the accommodation morphology of martensite variants from a self-accommodating state for the thermal martensite to an orientated stale for the stress-induced martensite. This observation led to the reconsideration of the criteria for pseudoelasticity. Quantitative expressions of criteria on both testing temperature and austenite yield strength were derived, which showed satisfactory agreement with experimental observations. (C) 1997 Acta Metallurgica Inc.