Microstructure, martensitic transformation and mechanical properties of Ni-Mn-Sn alloys by substituting Fe for Ni

The effects of partial substitution of Fe element for Ni element on the structure, martensitic transformation and mechanical properties of Ni50-xFexMn38Sn12 (x=0 and 3%, molar fraction) ferromagnetic shape memory alloys were investigated. Experimental results indicate that by substitution of Fe for Ni, the microstructure and crystal structure of the alloys change at room temperature. Compared with Ni50Mn38Sn12 alloy, the martensitic transformation starting temperature of Ni47Fe3Mn38Sn12 alloy is decreased by 32.5 K. It is also found that martensitic transformation occurs over a broad temperature window from 288.9 to 352.2 K. It is found that the mechanical properties of Ni-Mn-Sn alloy can be significantly improved by Fe addition. The Ni47Fe3Mn38Sn12 alloy achieves a maximum compressive strength of 855 MPa with a fracture strain of 11%. Moreover, the mechanism of the mechanical property improvement is clarified. Fe doping changes the fracture type from intergranular fracture of Ni50Mn38Sn12 alloy to transgranular cleavage fracture of Ni47Fe3Mn38Sn12 alloys.