微小重力環境下でのTb-Fe超磁歪合金の一方向凝固

抄録

TbFe₂ grain alignment in Tb-Fe alloys solidification under microgravity (μG) and terrestrial gravity (1G) was investigated. The microgravity was obtained by free fall in drop tower facility at the Japan Microgravity Center (JAMIC). TbFe_1.83 alloy of 1 gram was prepared for unidirectional solidification under microgravity environment. The samples were melted just before drop and solidified by contact chill against a sample under the microgravity during dropping. The microstructure of μG sample was columnar and TbFe₂ grains were strongly aligned along the thermal gradient. In 1G sample, the aligned microstructure was not obtained. The alloy composition was measured by EDX. The TbFe₃ phase was observed in 1G sample, and no TbFe₃ phase was observed in μG sample, caused by reduction of thermal convection in microgravity environment. In μG sample, the (111) orientation of TbFe₂ grains was obtained. The magnetostriction in parallel direction to the thermal gradient was larger than those in perpendicular direction in μG and 1G sample. The magnetostriction of μG sample in parallel direction to the thermal gradient was larger than that for 1G sample caused by microstructure.