Room temperature metamagnetic transformation of a tough dual-phase Ni–Mn–Sn–Fe ferromagnetic shape memory alloy

Achieving concurrent good mechanical and magnetic properties is highly desirable for ferromagnetic shape memory alloys for meaningful applications, yet is challenging due to the difficulty to combine ideal microstructure and magnetism in one. This work demonstrates an alloy design strategy to overcome this challenge in a Ni_51.5Mn_40-xFe_xSn_8.5 (x = 5, 6, 7) alloy system via microstructure engineering and composition tuning for its eutectic dual-phase microstructure. The alloys achieved a high strength of ∼2000 MPa and a ductility of ∼21%. In the meantime, the martensitic transformation was controlled within a particular temperature window between the Curie transition temperatures of the austenite and the martensite. This gives rise to the largest possible difference in saturation magnetization across the transformation and thus the highest driving force for the magnetic field mediated functionalities.