Martensitic transformation and magnetic properties in ferromagnetic shape memory alloy Ni43Mn46Sn11−xSix

This study investigated the effects of Si addition and heat treatment on the martensitic transformation and magnetic properties of Ni43Mn46Sn11−xSix (x = 1, 2, 3) alloys. The martensitic transformation temperatures were found to increase with increasing Si content in the alloy. A magnetic field-induced martensite-to-austenite transformation was found in Ni43Mn46Sn10Si1. Ageing of the Ni43Mn46Sn10Si1 alloy at 673 K resulted in the formation of a (Mn,Ni)–SiSn precipitate. The precipitate contains very low Sn content, causing the increase of the Sn content in the matrix phase and a decrease of martensitic transformation temperature. Ageing at 573 K is found to increase the Curie temperature and the saturation magnetization. This is attributed to the increase of atomic ordering of the matrix. Solution treatment of the aged samples at 1073 K was effective to restore the original transformation behaviour and magnetic properties.