Analysis of Martensitic Transformation in Ni-Mn-Sn FSMA

Abstract

Ferromagnetic shape memory alloys (FSMA) are a new class of potential multifunctional materials with advancement over the conventional heat-driven shape memory alloys due to their exceptional properties. FSMAs can be controlled by magnetic field have attracted considerable attention as a type of magnetic actuator materials. Among the Heusler alloys that exhibit magnetic shape memory effect, the most extensively studied are those of the Ni-Mn-Ga system. However, to overcome some of the problems related to practical application, such as the high cost of gallium and the low martensitic transformation temperature that they usually present, the search for Ga-free alloys has been recently attempted. This paper aims to represent the behavior of Ga free Ni-Mn-Sn Heusler FSMA by varying the weight percentage of Sn. Three alloys i.e. Mn50Ni50-xSnx (x = 5, 7.5, and 10) were produced as bulk polycrystalline ingots by arc melting. The structural austenite-martensite transformation was checked by Differential Scaning calorimetry (DSC). It is found that, the transformation temperatures gradually decrease as increasing the Sn content. Multiple martensitic transformations, such as two- or three-step martensitic transformations, occur in all these alloy systems. Microstructure and elemental composition of prepared specimen were examined by using a Scanning Electron Microscope (SEM) equipped with a microanalysis system. Therefore, the present Ga-free Ni-Mn-Sn Heusler FSMAs have the great possibility to use in high temperature application and can present a large magnetic-field-induced strain.