Vacuum Electromagnetic Levitation Melting and Undercooling of Peritectic Terfenol-D

摘要

For the first time, the undercooling of a magnetostrictive material-a near peritectic Tb_(0.27)Dy_(0.73)Fe_(1.90) alloy was realized by vacuum electromagnetic levitation melting and 60 K undercooling was obtained. There is one recalescence behavior during solidification of the undercooled melt, which can attribute to the priority precipitation of REFe_2 phase instead of REFe_3 phase, due to preferential nucleation and higher crystal growth rate of REFe_2 phase and the suppression of peritectic reaction. According to the crystal structural characteristics of REFe_2 and REFe_3, REFe_2 is a Laves phase intermetallics with MgCu_2 type structure, which has similar polytetrahedral structure with short range ordered structure in under-cooled melt and has lower potential harrier for nucleation than that of REFe_3, which lead to the preferential nucleation of REFe_2 phase directly from the undercooled melt. Also, the similarity of structures between REFe_2 phase and undercooled melt leads to higher crystal growth rate of REFe_2 phase than that of REFe_3.