Effect of grain size on superelasticity in Fe-Mn-Al-Ni shape memory alloy wire

Effects of grain size on superelastic properties in Fe-34Mn-15Al-7.5Ni alloy wires with a ⟨110⟩ fiber-texture were investigated by cyclic tensile tests. It was confirmed that the critical stress for induced martensitic transformation and the superelastic strain are functions of relative grain size d/D (d: mean grain diameter, D: wire diameter), and that the critical stress is proportional to (1–d/D)2 as well as in Cu-based shape memory alloys. A large superelastic strain of about 5% was obtained in the specimen with a large relative grain size over d/D = 1.