Orientation Analysis of Hexagonal Dendrite Formed from an Undercooled Melt of α-Fe2Si5

Abstract

In order to elucidate the solidification process of anisotropic intermetallic compounds in the undercooled melt, the containerless solidification of a-Fe 2 Si 5 was conducted using an electromagnetic levitator with a high-speed video (HSV) recorder. With increased undercooling, the shape of the growing crystal drastically changed from a polyhedron-type crystal to a swordlike dendrite crystal. Notably, the swordlike crystal shows sixfold symmetry, despite the tetragonal structure of a-Fe 2 Si 5 . The growth velocity analysis based on the dendrite growth model suggests that the interfacial attachment kinetics dominantly controls the growth process. Moreover, based on the analysis of crystallographic orientation using an electron backscattering pattern (EBSP) apparatus, we propose that the sixfold symmetry resulted from the three different crystals growing into the 110 h i direction of the (111) plane of the metastable cubic phase of c-FeSi 2 .