In situ scanning electron microscopy study of the thermoelastic martensitic transformation in Ti-Ni shape memory alloy

The thermoelastic martensitic transformation from the B2 to B19' structures in the Ti-Ni shape memory alloy was observed by in situ scanning electron microscopy in order to investigate the self-accommodation microstructure. Nucleation of the V-shaped habit plane variant cluster (2HPVC) triggers the formation of the hexangular HPVC (6HPVC) that is formed by six habit plane variants in the grain interior. The triangular morphology (3HPVC) is a derivative of 2HPVC. The autocatalytic transformation spreads from the 6HPVCs to the grain boundary and the reverse transformation proceeds like a rewind of the forward transformation. 2HPVC and 6HPVC are the most favorable morphologies for nucleation and growth, respectively, as explained by the analysis of the kinematic compatibility at junction planes. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.