Investigation of the effect of gadolinium rare earth element on transformation temperature and physical properties of NiMnSn magnetic shape memory alloys

With the development of technology in recent years, the development of smart materials has gained speed. Magnetic shape memory alloys, which are a strong alternative to shape memory alloys, one of the subgroups of smart materials with a wide field of study, have been the focus of attention. While the recovery of traditional shape memory alloys occurs with temperature, it is known that it also occurs with magnetic field in magnetic shape memory alloys. In this study, the rare earth element Gadolinium (Gd) was added to the NiMnSn alloy, which is an alternative to the NiMnGa alloy group. Since rare earth elements have strategic importance for our country in recent years, Gd element has been preferred in this thesis study. In this study, the phase transformation temperatures of the alloys were determined by the Differential Scanning Calorimetry (DSC), which is a thermal analysis method. According to the thermal analysis measurement results, it was observed that increasing gadolinium ratio decreased the austenite↔martensite transformation temperatures of the NiMnSn alloy. X-rays and SEM-EDX analysis were performed to determine the morphological properties of the crystal structure and microstructure of the alloys. It has been determined that the alloys have a precipitate phase other than austenite and martensite phase. However, when the electrical resistance of the alloys were measured against temperature, it was observed that the electrical resistance hysteresis decreased with the addition of Gadolinium.