Martensitic and magnetic transformation of Co41Ni32Al24Sb3 and Co41Ni32Al27 alloys

Abstract The martensitic transformation and magnetic property of Co 41 Ni 32 Al 27 and Co 41 Ni 32 Al 24 Sb 3 alloys were investigated by optical microscopy(OM), scanning electric microscopy(SEM), energy dispersive X-ray spectroscopy(EDS), X-ray diffractometry (XRD), differential scanning calorimeter analysis(DSC) and vibration sample magnetometer(VSM) methods. The results show that martensitic crystal structure of Co 41 Ni 32 Al 24 Sb 3 alloy is still L1 0 type. Both martensitic transformation temperature T m and Curie point T c are in linear relation to quenching temperature. T m increases by 9 K and T c increases by 7.5 K for every 10 K increasing in quenched temperature. Quenched from same temperature, T m of Co 41 Ni 32 Al 24 Sb 3 alloy is higher than that of Co 41 Ni 32 Al 27 alloy by 76 K, meanwhile T c is higher by 18 K. The melting point of Co-Ni-Al alloy is decreased by the Sb addition, eutectic structure appears in Co 41 Ni 32 Al 24 Sb 3 alloy annealed at 1 573 K, which indicates that the alloy is partially melted, whereas Co 41 Ni 32 Al 27 alloy can be annealed at 1 623 K without melted. The martensitic transformation temperature range of Co 41 Ni 32 Al 24 Sb 3 alloy is 22–29 K, only half that of Co 41 Ni 32 Al 27 alloy. This is a very important result to benefit the achievement of large magnetic field induced strain on Co-Ni-Al based alloy. The results of Tm and Tc were explained by total average s+d electron concentration and magnetic valence number Z m respectively.