Microstructure、Mechanical Properties and Corrosion Behaviour of Polycrystalline Nicomnsngd Heusler Alloys

The microstructure, martensitic transformation, mechanical properties and corrosion resistance of Ni45Co5Mn38Sn12-xGdx (x = 0.3, 0.6, 1, 1.5at%) magnetic shape memory alloy have been systematically investigated. When the Gd doping amount is 0.3 at%, some gray mottled phases appear in the alloy matrix, and there are white particle phases around the gray speckle phases. As Gd doping content continues to increase, the gray mottled phases and white particle phases gradually join together distributing along the grain boundaries. These alloys present 10M orthorhombic martensite at room temperature. Both 10M orthorhombic martensite and 14M monoclinic martensite exist Ni45Co5Mn38Sn10.5Gd1.5 alloy. The valence electron concentration increases and the phase transition temperature increases as a result of Gd doping. The compressive strength and strain of the alloy are significantly enhanced by the incorporation of Gd. When the Gd content is 1.5 at %, the compressive strength of the alloy is up to 1258 MPa and the compressive strain reaches to 13.72%. The doping of Gd enhances the seawater corrosion resistance of NiCoMnSn alloy. Moreover, NiCoMnSnGd alloys have better seawater corrosion resistance than 304 stainless steel.