To improve the shape memory effect, the solutionized Fe-24Mn-6Si-9Cr-6Ni alloy was shot peened and subsequently annealed. The phase constituent was examined using the X-ray diffraction method. Microstructure evolution was characterized using an optical microscope and the electronic backscatter diffraction method, and the shape memory effect was evaluated using a bending test. The results show that α′-martensite and ε-martensite were introduced into the shot-peened surface layer. The α′-martensite remained after annealing even at 850 °C. Microstructure of the surface layer was refined through shot peening and subsequent annealing. Compared with those of the solutionized specimen, the shape recovery ratio and recovery strain of the specimens that are shot peened and subsequently annealed are significantly improved at different prestrains.

NbC precipitation in Fe–Mn–Si-based alloys is an effective method to improve the shape memory effect. In this study, the precipitation behavior was investigated using a thermodynamical model to understand the mechanism and optimize the precipitates for a better performance of Fe–Mn–Si-based shape memory alloys. The influence of alloying elements can be considered in the model by introducing interaction parameters. The precipitate size distribution, mean size, precipitate volume faction, and number density of three typical Fe–Mn–Si-based alloys with different NbC addition amounts were calculated. The results indicated that the mean size could be decreased significantly as the NbC addition increased from 0.5% to 1.0%, while the precipitate volume fraction and number density showed obvious increments. The Fe–28Mn–6Si– 5Cr alloys exhibited smaller mean sizes and higher number densities than the Fe– 14Mn–6Si–9Cr–5Ni and Fe–21Mn–6Si–9Cr–5Ni alloys. It was also found that the precipitate size distribution showed no evident change as the aging time increased from 0.5 h to 2 h except for the Fe–28Mn–6Si–5Cr–0.5NbC alloy in which the precipitates began to coarsen after about 1.25 h.