Larger Recovery Strains in Cast Fe–Mn–Si‐Based Shape Memory Alloys by Reducing Thermal Activation and Optimizing Mn Content

Previous work shows that a maximal recovery strain of 8.4% after being bent at room temperature is realized in annealed cast polycrystalline Fe–Mn–Si‐based alloys because of the reduced annealing twin boundaries. Theoretically, higher recovery strains can be expected at cryogenic deformation by reducing thermal activation. To confirm this idea, martensitic transformation behaviors and the recovery strains after being bent at 77 K are investigated in the cast Fe–(20–26)Mn–5.5Si–8.5Cr–5Ni alloys. Herein, larger recovery strains as high as ≈10.0% are realized in an annealed cast Fe–23Mn–5.5Si–8.5Cr–5Ni alloy after being bent at 77 K. The reduced thermal activation together with suppressed formation of thermal‐induced martensite by optimizing Mn content can account for the larger recovery strain. In these results, a new avenue is opened up for further enhancement of the recovery strain in Fe–Mn–Si‐based shape memory alloys.