Phase-field simulations of precipitation induced high dissipative superelasticity at low temperatures in shape memory alloys

Shape memory alloys (SMAs) typically lose superelasticity completely below the martensitic transformation finish temperature (M_f) due to detwinning-dominated deformation, which limits their reversible strain capabilities under loading and unloading. Here, using phase-field simulations, we introduce a novel mechanism for precipitation-induced reversible martensitic domain switching to achieve superelasticity below M_f. This mechanism enables precise control over energy dissipation and recoverable strain by tuning precipitation configurations, to transform the behavior of SMAs at low temperatures. Remarkably, we demonstrate that gradient-distributed, variant-selective precipitate condition can resolve the challenge of combining high superelasticity with significant dissipation in martensitic transformations below M_f. Furthermore, our simulations reveal that the critical stress for superelasticity at low temperatures deviates from the traditional Clausius-Clapeyron relationship, due to recoverable domain switching between different martensitic variants. Further analysis reveals that the recoverable domain switching at low temperatures is driven by an intrinsic restoring force arising from the confinement between short-range ordered (SRO) martensitic domain regions and long-range ordered (LRO) martensitic domain regions, induced by gradient-distributed, variant-selective precipitate conditions. This confinement stabilizes specific martensitic variants, enabling significant recoverable strain during loading and unloading, which in turn contributes to the observed high energy dissipation. Our work provides a new strategy for enhancing the functionality and versatility of SMAs in demanding environments.