Elastic micro-strain energy of austenite-martensite interface in NiTi

The interfacial energy due to elastic micro-strains at the austenite-twinned martensite interface is calculated for the NiTi shape memory alloy undergoing cubic-to-monoclinic B2 <-> B19' transformation. For each crystallographically distinct microstructure, an energetically favourable local shape of the interface is determined. The approach employs finite element computations and energy minimization with respect to shape parameters, taking into account elastic anisotropy of the phases and finite-strain kinematics. The effect of atomic-scale interfacial energy is studied.