Formation mechanism of Fe₈₀Si₈B₁₂ metallic glass

Abstract

In order to gain an understanding of the glass-forming mechanism during the rapid quenching of a metallic alloy, the nucleation and growth process of the crystalline phase which competes with the metallic glass must be investigated. The microstructures of melt-spun Fe₈₀Si₈B₁₂ alloy ribbons with different thicknesses were examined using optical and electron microscopy. The phase competing with the metallic glass isα-(Fe, Si) ferrite, nucleated by the homogeneous nucleation. The growth process ofα-(Fe, Si) dendrites was explained well by Liptonet al.'s theory of dendritic growth in an undercooled alloy melt. It was concluded that the easy glass-forming ability during rapid quenching of the Fe₈₀Si₈B₁₂ alloy is due to (i) the slow growth rate ofα-(Fe, Si) dendrite, and (ii) the wide gap between the temperatures of the maximum nucleation rate and the maximum growth velocity.