INVESTIGATION ON MARTENSITIC TRANSFORMATION AND MECHANICAL PROPERTIES OF THE Ni50Mn37-xSn1.3Fex(x=0, 2,5,10) ALLOYS

摘要

The microstructures, martensitic transformation behavior and mechanical properties of Fe-doped Ni-Mn-Sn ferromagnetic shape memory alloys are investigated. The influence of composition on the precipitation of second phase and the improvement of ductility are also explained in this paper. The results show that the phase transformations of Ni-Mn-Sn-Fe alloys are still one-step thermo-elastic transformation. The transformation temperatures increase with the increase of Fe content, and the hysteresis decreases after being doped Fe element, this is mainly due to the difference of atom size and the precipitation of second phase. After homogeneously annealing at 1123K for 12h, the Ni50Mn35Sn13Fe2 alloy becomes single phase due to the solid solubility of Fe. The breaking strength and maximum compressive strain increase with the increase of doped Fe content due to the solid solution strengthening and second phase strengthening. The fracture of the Ni-Mn-Sn alloy is intergranular crack, and becomes transgranular crack after doping Fe element. The ductility is improved by this means, which is in favour of the application of the Ni-Mn-Sn alloys.