Study of Martensitic Transformation Temperatures of Ferromagnetic Shape Memory NiMnGa Alloys

As a new class of shape memory alloy, Ni2MnGa ferromagnetic shape memory alloy (FSMA) has both large reversible strain and higher response frequency, which has attracted considerable attention and has been widely investigated.The martensitic transformations temperatures of the as-cast Ni2MnGa alloys are investigated by differential scanning calorimeter (DSC). Following conclusions were obtained from experimental results: By using DSC measurement, martensite transformation temperatures (including Ms, Mf, As and Af) were obtained in two alloy series of Ni51.5+xMn23.5Ga25-x and Ni51.5Mn23.5+yGa25-y. Results showed that: martensite transformation temperatures enhanced with the Ni and Mn increasing respectively, and the effect is stronger for Ni than Mn. After 600°C vacuum annealing 6h using powder samples, the martensitic transformation temperature was slight lower than as-cast state.