Microstructure, martensitic transformation and mechanical properties of Ni50Mn30Ga20−xCux ferromagnetic shape memory alloys

The effect of partial substitution of Cu for Ga on the microstructure, martensitic transformation and mechanical properties of Ni50Mn30Ga20−xCux alloys was investigated by optical microscope (OM), different scanning calorimetry (DSC) and X-ray diffraction (XRD). The results show that the Ni50Mn30Ga20−xCux alloys exhibit thermoelastic martensitic transformation. The martensitic transformation temperatures of the Ni50Mn30Ga20−xCux sample increase remarkably with increase of Cu content, while the martensite structure of these alloys changes from 7 M to non-modulated T martensite at room temperature. In addition, the compressive strength and fracture strain of alloys are clearly enhanced with increase of Cu content, which can be attributed to the strengthening of solution.

► The Ni50Mn30Ga20−xCux alloys exhibit thermoelastic martensitic transformation.
► Martensite changes from 7 M to non-modulated T martensite with increasing Cu content.
► The compressive strength and fracture strain are enhanced with increasing Cu content.
► The highest compressive strength of 3178.9 MPa is obtained in Ni50Mn30Ga16Cu4 alloy.