The suppression and recovery of martensitic transformation in a Ni–Co–Mn–In magnetic shape memory alloy

The intrinsic mechanism of the martensitic transformation (MT) suppression observed in Ni–Co–Mn–In alloys fabricated under non-equilibrium conditions still remains mysterious. Here, we used the undercooling technique to obtain a solidified microstructure in non-equilibrium state, subsequently leading to MT suppression even further cooling to 10 K. It was found that primary dendrite-like In-depleted precipitates occurred during solidification under a large undercooling. After a prolonged annealing, the MT interestingly appeared again due to the dissolution of the precipitates and the recovery of equilibrium chemical composition in the matrix.

► We used the undercooling technique to obtain a solidified microstructure in non-equilibrium state. ► Primary dendrite-like In-depleted precipitates occurred during solidification under a large undercooling, subsequently leading to MT suppression. ► After a prolonged annealing, the MT appeared again due to the dissolution of the precipitates and the recovery of equilibrium chemical composition. ► We establish the relationships among non-equilibrium solidification with different undercoolings, martensitic transformation and magnetic behaviors.