T. Todaka, M. Sonoda, Y. Sato, M. Enokizono, Oita University, Oita, Japan
Ferromagnetic shape memory alloys have been developed by means of the melt spinning technique in air. The alloys are multi-functional materials, which have both the ferromagnetic property and shape memory property. If we can simultaneously improve the material properties, the applications of the shape memory alloys will be widened dramatically in the field of the magnetic sensors and actuators. Also contact-less induction heating techniques can be used readily in returning procedure to be a shape before deformation because the heating efficiency becomes higher due to the high permeability.
We have focused on Fe-Mn-Si based alloys, which are nonmagnetic material due to high manganese content (28-34Mn, 4-6.5Si wt%). To improve ferromagnetic function, we have investigated to add rare earth elements such as Nd, Sm, and Tb. The results show that the ferromagnetic functions were improved by adding the rare earth elements. Also we have added Cr to improve corrosion resistance, to make ribbon samples directly by means of the melt spinning technique in air. Advantage of the melt spinning technique is that we can easily produce a large amount of ribbon and improve shape memory property by changing the crystal condition. As a result, we have found out that the saturation magnetization after shape memory treatment increases by adding rare earth elements. Addition of 0.5 - 1.0 wt% Sm or Tb was most effective in increasing the saturation magnetization. However, brittleness of the samples was not so good and it was difficult to evaluate the shape memory property by using shape recovery strain measurements. In this paper, the measured properties of the Fe-Mn-Cr-Si-R-B alloys are compared in detail.
Summary: This paper presents measured magnetic and shape memory properties of Fe-Mn-Cr-Si-R-B ribbons developed by means of the melt spinning technique in air. Here, R means a rare earth element. The alloys are multi-functional materials, which have both the ferromagnetic property and shape memory property. If we can simultaneously improve the material properties, the applications of the shape memory alloys will be widened dramatically in the field of the electromagnetic sensors and actuators. In order to improve ferromagnetic function of the Fe-Mn-Si based alloys, we have investigated to add rare earth elements. In this paper, measured magnetic and shape memory property of Fe-Mn-Cr-Si-R-B alloys were discussed.
