Thermal analysis, crystal structure and magnetic properties of Cr-doped Ni-Mn-Sn high-temperature magnetic shape memory alloys

Abstract

The superiority of NiMnSn alloy on NiMnGa alloy is far ahead in term of some physical characteristics, and therefore, the development of this alloy group is very important. In this work, Ni50Mn45-xSn5Crx magnetic shape memory alloys were produced for x=0, 4, 6, 10 and 12. Thermal analysis was performed on produced alloys in a wide range (200-1000 degrees C) by using differential scanning calorimetry, thermogravimetric and differential thermal analysis. According to the thermal analysis results, the austenite <-> martensite transformation temperatures of the NiMnSn alloy decreased with increasing chromium content. Furthermore, the increase in the chromium ratio caused single-phase transformation due to the multiple phase transformation that was observed in the NiMnSn alloy. In addition, the crystal structure and microstructure analyses of the alloys were determined by using X-ray diffraction and scanning electron microscopy-energy-dispersive X-ray spectroscopy. In all cases, martensite and gamma phase were encountered and the gamma phase ratio was found to be increased by chromium addition. The magnetization characteristics were studied by using physical properties measurement systems device, and it was found that the alloys have a considerably small response to magnetic flux.