Interplay of martensitic phase transformation and plastic slip in polycrystals

We study the interplay between martensitic phase transformation and plastic slip in polycrystalline media. The work is motivated by the phenomenon of superelasticity – the ability of the material to recover strains beyond their apparent elastic limit – observed in shape-memory alloys. Often the recovery is not perfect with residual strain after a deformation and recovery cycle, and the stress–strain curve changes with cycling. We develop a mesoscale model at the single crystal level, and use it to study polycrystals. The model is able to reproduce various observations and provide important insight into the interplay. In particular, we show that transformation and plasticity can occur synergistically, with plasticity providing a mechanism for bridging across poorly oriented and thus non-transforming grains.