Yuji Sutou

Magnetic field-induced reversible actuation using ferromagnetic shape memory alloys

Abstract This paper presents a simple method to examine whether a ferromagnetic shape memory alloy can be used as an actuator by controlling the transformation temperature by magnetic field. Both Fe–Pd and NiAlCo alloys are studied. The analysis results show the recently discovered alloy of NiAlCo cannot be used. Although an Fe–Pd alloy can be used, in principle, for magnetic field actuation, the work extracted by magnetic actuation is small.

Martensitic transformation behavior under magnetic field in Co-Ni-Al ferromagnetic shape memory alloys

Effect of the magnetic field on the martensitic transformation of Co-Ni-Al single-crystal was investigated by differential thermal analysis (DTA) and the in-situ microstructure observation under magnetic field. The martensitic transformation temperatures Ms and Mf of the Co34.5Ni35.5Al30 single-crystal specimen showing the martensitic transformation from the paramagnetic austenite (B2) to the ferromagnetic martensite slightly increased under the magnetic field and those temperature shifts were about 1.3°C at 1.0T. It was also observed in the Co34.5Ni35.5Al30 single-crystal specimen that the phase boundaries between the austenite and the martensite slightly move by applying the magnetic field of 1.0T. These results are discussed on the basis of a thermodynamic stabilty of the martensite phase under the magnetic field. The martensitic and the magnetic transformation behaviors of the Ni-Al-Co alloys are also reviewed.