Martensite reorientation after thermal cycling in NiTiCu shape memory alloys studied by EBSD technique

Abstract

The Ni25Ti50Cu25 shape memory alloy exhibits one-step martensitic transformation. Transformation occurs between the B2 parent phase and the B19 orthorhombic martensite. The course of the martensitic transformation was in situ studied in the alloy with use of electron backscatter diffraction. During heating, reverse martensitic transformation occurs from the B19 orthorhombic martensite to the B2 parent phase. On cooling, from the parent phase the B19 martensite is formed. Obtained results proved that the B19 martensitic plates forms the variants indexed as 1, 3, and 5. Thermal cycling does not change the crystallographic correlation between the parent phase and the martensite. However, after cycling, different rearrangement of the martensitic plates can be received. In consequence, characteristic temperatures of the martensitic transformation are shifted.