Sharp Phase front model of phase transformation and micro-macro transitions in shape memory alloys

摘要

This paper deals with the micro-macro transition in shape memory alloy thin films using a recently developed sharp phase front-based three-dimensional (3D) constitutive model outlined by Stoilov (2002), and originally proposed in the 1D context by Stoilov and Bhattacharyya (2002). The key ingredient in the model is the recognition of austenite and/or martensite variants as separate phases in a SMA domain. Evolution of the interface between these phases is taken as an indicator of a phase transformation in progress. A generalized Clausius-Clapeyron (CC) equation is derived from the continuity of chemical potential at the interface. The implications of the CC equation on the initiation of phase transformation are studied for various mechanical loading modes. Finally, the issue of micro-macro transition is examined in the context of stress-strain-temperature response of a CuAlNi SMA thin film.