Morphological Characteristics of the Orthorhombic Martensite in a Shape Memory Ti–Ni–Cu Alloy

Morphological characteristics of the orthorhombic martensite in a Ti–Ni–Cu shape memory alloy have been investigated and the following have been found: (1) In the cubic (B2) to orthorhombic transformation of the Ti–Ni–Cu alloy, no lattice invariant shear is needed. This is due to the fact that one of the principal distortion of transformation is nearly zero. (2) The experimentally obtained habit planes are {334} of the parent lattice and agree very well with the prediction by the phenomenological theory of martensite. (3) Self-accommodation in the orthorhombic martensite is achieved by combination of three variants around each one of the ‹111› axes of the parent latice.