Microstructure, superelasticity and fracture behavior in magnetic shape memory Co–Ni–Ga–Fe alloys with two-phase structures

It is shown that the martensitic transformation temperatures of Co50Ni22−xGa28Fex (x = 0, 1, 2, 5) alloys decrease as Ni is gradually substituted by Fe. The volume fraction of the second phase is also reduced with increasing Fe content, which impairs the mechanical properties. Two-phase Co–Ni–Ga–Fe alloys exhibit complete superelastic behaviors in a wide temperature interval between room temperature and 200 °C. Moreover, the stress hysteresis in two-phase alloy shows much stronger sensitivity to temperature than that in single-phase alloy.