Phase Formation in Undercooled Sm–Co Alloy Melts

Abstract

Sm_xCo_100−x alloy melts (x = 10.5, 12.5 and 17 at.%) are processed containerlessly by electromagnetic levitation and drop-tube technique in order to get access to the metastable state of the undercooled melt. By dint of undercooling non-equilibrium phase formation is facilitated. The solidified specimen are subsequently analyzed by electron microscopy, X-ray diffraction and thermal magnetic analyses. The results show that different types of solidification behaviors are observed depending on alloy composition and undercooling level prior to solidification. Bulk samples processed by electromagnetic levitation technique are solidified by primary formation of either Sm₂Co₁₇ or SmCo₅, whereas primary phase formation of metastable SmCo7 is detected in small particles attained by drop-tube processing where cooling rates lie in the order of 10³–10⁵ K/s.