Synthesis and structural studies of Ni-Mn based Heusler shape memory alloys

Abstract

Ni-Mn based Heusler shape memory alloys are type of smart materials which possesses both ferromagnetic and shape memory properties. Due to multifunctional properties these materials have increased significant interest for the applications in actuators, sensing devices and magnetic refrigeration. The aim of this work was to synthesize and structural study of Ni-Mn-Sn and Ni-Mn-Al alloys which have recently emerged as Gallium-free shape memory alloys. Two alloys Ni48Mn26Sn26 and Ni51Mn26Al23 (at %) were synthesized using vacuum arc remelting technique under an argon gas atmosphere to improve homogeneity of the alloys. The structural studies of the prepared alloys were conducted and compared using X-ray Diffraction (XRD) and scanning electron microscope (SEM) coupled with Energy -dispersive X-ray spectroscopy (EDX). The results revealed that an average crystallite size of Ni-Mn-Al was smaller than Ni-Mn-Sn alloy. The morphology showed an average particle size of 5-6 μm and 0.6-0.7 μm for Ni-Mn-Sn and Ni-Mn-Al alloys respectively. Magnetic behavior studied by Vibrating sample magnetometer (VSM) showed soft magnetic behavior of the alloys. The synthesized alloys have exhibited and confirmed closely matching stoichiometric composition of Heusler shape memory alloys (X2YZ) with no contamination.