Microstructural characterization and superelastic response of a Ni50.3Ti29.7Zr20 high-temperature shape memory alloy

The microstructure and superelastic response of a Ni50.3Ti29.7Zr20 high-temperature shape memory alloy were studied. The alloy exhibited a recoverable strain level of 5% at 170 degrees C and near-perfect superelasticity up to 250 degrees C under 3% applied strain when fine precipitates were present. In this case, large martensite variants easily formed during the stress-induced martensitic transformation while dislocation motion was impeded. In contrast, poor superelastic response was obtained in samples containing large particles that constrain martensite formation to channels between elongated precipitates. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.