Tuning effect of Cu doping on martensitic transformation and magnetic and mechanical properties of Heusler alloy Mn50Ni40In10−xCux (x = 0–10) ribbons

Single-phase Mn50Ni40In10−xCux (x = 0, 1, 2, 4, 6, 8, and 10) Heusler alloys were synthesized by melt-spinning method. Martensitic transformation is retained within the whole composition range studied. The substitution of Cu for In leads to a drastic increase in the martensitic transformation temperature TM from below room temperature to above 750 K, and enhances the antiferromagnetic character of the martensite. The increase in TM is related to the increasing electron concentration e/a and decreasing cell volume V with Cu doping. The energy difference between martensite and austenite also increases with Cu doping, which tends to elevate the TM. Cu doping can enhance the metallic bonding character in NiMn-based magnetic shape memory alloys (MSMAs) and is a grain refining strategy of their ribbons. The oriented columnar grains in In-rich samples change to fine equiaxial grains in Cu-rich samples. All this has a positive effect on the strength and ductility. The tensile strength of the Mn50Ni40Cu10 ribbon is 3.6 times higher than that of Mn50Ni40In6Cu4. So, Mn–Ni–Cu can be a promising all-d-metal Heusler alloy platform for developing MSMAs with interesting properties.