Effect of Ni, C and Ti Addition on Shape Recovery Behavior and the Mechanical Properties of Fe-17Mn-5Si-5Cr Shape Memory Alloys

Fe-Mn-Si based shape memory alloy is a new functional material that can be used to apply prestress to civil and structural components such as concrete structures. In this study, the effects of alloying elements Ni, C and Ti on the mechanical and shape memory properties of the alloy were investigated in detail using a base alloy composition of Fe-17Mn-5Si-5Cr (wt%). Enhanced shape recovery ratio and decreasing strength were observed in the alloy when 4 wt% Ni was added. With the further addition of 0.05 wt% C, the alloy showed even higher shape recovery behavior, although the mechanical strength was lowered by the C addition. Increasing the carbon content up to 0.1 wt% led to higher mechanical strength while the shape recovery ratio was decreased slightly. It was shown that the addition of 1 wt% Ti can significantly enhance the shape recovery behavior of the alloy. The recovery behavior of the alloy with the co-addition of 0.3 wt% C and 1 wt% Ti was similar to the alloy without Ti but containing 0 1 wt% C, even though the C content was significantly higher. The alloy with the co-addition of 0.3 wt% C and 1 wt% Ti has great potential as functional components in prestressed civil engineering structures, since the yield strength of the alloy is as high as 400 MPa in the solution heat treated condition and can be further improved by aging heat treatments, which precipitate TiC particles.