Research on Development of Ferromagnetic Shape Memory Alloy

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This research has been carried out to develop a new ferromagnetic shape memory alloy, which has both ferromagnetic property and shape memory effect itself. Firstly we have discovered Fe62-Cr13-Co10-Ni7-Si6-Mn2[wt%] alloy in trial and error. In this composition, we were able to improve the shape memory effect(SME) by heat treatment, however the ferromagnetic property deteriorated in the same time. In the similar system without cobalt, we have optimized the composition ratio. As a result, Fe68-Cr13-Ni7-Si6-Mn6[wt%] alloy showed an excellent SME(100%) and its saturation magnetization Ms was equal to 65.8 [emu/g]. In this research, we have made clear the role of each component, that is, influence of each element on the magnetic properties and the shape memory properties. The new ferromagnetic shape memory alloys have been produced by means of the melt spinning technique. The condition how to produce the ribbon, which contains higher manganese composition over 14%, has also clarified.In addition, we have investigated to add rare earth elements for the Fe-Cr-Si-Mn system. The samples without heat-treatment, had higher saturation magnetization over 80[emu/g] by adding nearly one percent of a rare earth element, however the magnetic property deteriorated after the heat-treatment in similarly. After optimisation, we have found out that Fe58.1-Mn26-Cr10-Si5-Nd0.7-B0.2[wt%] alloy had the perfect SME (100%) and the high saturation magnetization over 60[emu/g](under rapid cooling after heating at 970℃ for 30 seconds) and Fe57.9-Mn26-Cr10-Si4.9-Sm1-B0.2[wt%] alloy had the perfect SME(100%) and the high saturation magnetization over 87.9[emu/g](under rapid cooling after heating at 910℃ for 40 seconds). The materials developed in this research have wide application in the field of the magnetic sensors and actuators.