Dynamic strain loading of cubic to tetragonal martensites

We present three-dimensional simulations of the microstructure and mechanical response of shape memory alloys undergoing cubic to tetragonal transitions, using FePd as an example. The simulations are based on a nonlinear elastic free-energy in terms of the appropriate strain fields. The dynamics is simulated by force balance equations for the displacement fields with a damping term derived from a dissipation function. Stress-strain properties in the pseudoelastic as well as the shape memory regime are investigated using strain loading. We also study the effects of defect-induced heterogeneous nucleation and motion of twin boundaries during deformation. Thus, we probe the influence of the microstructure on the mechanical response and investigate how the stress-strain behavior changes as a function of strain rate.