Ferrous Shape Memory Alloys

“Shape memory” describes the recovery of shape with an apparently permanent strain by heating (shape memory effect: SME) or removal of stress (superelasticity: SE). Fe–Ni–Co–Al–(Ta, Nb, or Ti) and Fe–Mn–Al–Ni alloys exhibit SME and SE associated with FCC/BCT and BCC/FCC martensitic transformations, respectively, and suitable microstructural controls are important. Fe–Mn–Si alloys using reversible FCC/HCP martensitic transformation show good low-cycle fatigue and SME, and have been practically applied to a seismic damping component for building. In this article, the Fe–Ni–Co–Al–, Fe–Mn–Al–Ni–, and Fe–Mn–Si-based alloys, which have been recently developed, are introduced.