Investigation of twin boundary thickness and energy in CuAlNi shape memory alloy

The nanometer-scale thickness and energy of twin boundaries govern the martensitic twin structure and its dynamics, which are responsible for the actuation and superelasticity of shape memory alloys. In this letter the authors apply a method, which has been recently developed for investigating twin wall structures in ferroelectric crystals, on a shape memory alloy crystal. Fittings of simulated displacement fields to atomic force microscopy measurements allow them to extract the thickness of type-I twin boundaries in CuAlNi. Further, a relation between the twin boundary thickness and energy is developed and used for evaluating the twin boundary energy. (C) 2007 American Institute of Physics.