Improvement of shape memory properties of NbC containing Fe–Mn–Si based shape memory alloys by simple thermomechanical treatments

A systematic study of effect of pre-deformation before aging on shape memory properties in Fe–Mn–Si based alloys containing Nb and C has been performed and it is found that the room temperature (RT) deformation as well as deformation at high temperature in the austenitic range can greatly improve shape memory effect (SME). The results on two representative NbC containing alloys, i.e., Fe–28Mn–6Si–5Cr–0.53Nb–0.06C and Fe–15Mn–5Si–9Cr–5Ni–0.53Nb–0.06C (mass%) are as follows: (1) about 90% shape recovery for 4% initial strain and 250–320 MPa shape recovery stress are obtained for pre-rolling by 10–30% at 870 K and (2) in the case of pre-rolling at room temperature, 75% shape recovery for 4% initial strain is obtained with 10% rolled samples and 240–320 MPa shape recovery stress is attained for 10–30% rolling. The improved shape recoveries are fairly close to those of the trained conventional shape memory alloys (SMAs) without NbC and their shape recovery stresses are nearly twice those of the trained ones.