Factors affecting recovery stress in Fe–Mn–Si–Cr–Ni–C shape memory alloys

Abstract

The effects of the heating temperature, the carbon content, the amount of pre-strain, the annealing temperature, and the conventional training on the recovery stresses at room temperature of cold-drawn Fe–Mn–Si–Cr–Ni–C shape memory alloys were studied. The results showed that the addition of carbon or the refining of grains could more significantly enhance the recovery stress than the conventional training. The recovery stress of a cold-drawn Fe–Mn–Si–Cr–Ni alloy with 0.18%C could reach 565MPa only after annealed at 1023K. Its recovery stress was only improved to 452MPa after it was subjected to annealing at conventional temperature 1373K and then four cycles of the conventional training. The dominating factors affecting the recovery stress were the amount of the plastic deformation and that of the martensitic transformation induced by the recovery stress in cooling, not the recovery strain under no constraints.