Eutectic(alpha-Fe2Si5, epsilon-FeSi)に現れる3層構造

Abstract

Stoichiometrically mixed (FeSi2) Fe and Si powders were melted in a tri-arc furnace in an argon atmosphere and were allowed to cool naturally to room temperature and a eutectic crystal of epsilon-phase embedded in alpha-phase of iron silicide was obtained. Three kinds of layers were determined: the grain size of epsilon-phase was more than 100 micrometers, about 50 micrometers and less than 1 micrometer. Only the first layer did not contain alpha-phase. The interfaces between the layers were so definite that the grain size was changed abruptly between the layers. When the crystal was annealed in vacuum at 1,150 K for 70 h, the last two layers were transformed to beta-FeSi2 but the bottom layer containing only epsilon-phase was not changed by the thermal treatment.