Martensitic transformation and mechanical properties in Ni-Co-Mn-In-Gd metamagnetic shape memory alloys

The influences of rare earth element Gd on martensite phase transformation, microscopic structure and mechanical performance of the Ni45Co5Mn37In13-xGdx alloys have been studied. The Gd-rich phase is formed due to the doping of Gd. With the increase of the Gd content, the quantity and size of the Gd-rich phase increase, whereas the martensite does not change exhibiting seven-layered structures. The doping of Gd not only notably increases the compressive strength and elongation, but also raises the martensitic transformation temperatures. The biggest compressive strength (992 MPa) is gained in the Ni45Co5Mn37In11Gd2 alloy about 5.5 times that of the Ni45Co5Mn37In13 alloy. The compressive elongation rises obviously with the increase of the Gd content, and reaches the maximum value 8.8% when the Gd content is 1 at%.