Properties of Ni-Fe based shape memory Heusler alloys

Abstract

Theproject investigates the effect of partial replacement of Iron (Fe) with Nickel (Ni) in Ni2FeGa Heusler type Shape Memory alloy to understand its effect on the Martensitic transformation. Literature reports on stoichiometric Ni2FeGa report a secondary phase formation in this compound. Thus the broader aim of the project includes understanding this secondary phase, its influence on the martensitic transition, if any, and means to control its phase fraction. Accord ingly, the compositions with varying Ni:Fe ratios were prepared using arc melt ing technique and studied for their crystal structure, micro-structure, and phys ical & magnetic properties. For this, X-Ray diffraction was carried out on all the samples, and it showing L21 to L12 structural progression with increasing replacement of Ni with Fe. The micro-structural analysis was carried out using scanning electron microscopy (SEM). The SEM images show dendritic struc tures of this secondary phase. Variation of electrical resistivity with temperature shows distinct signatures often associated with a martensite transition.