Eutectic compositions in potentially glass forming binary or ternary alloy systems are usually the starting point to identify metallic liquids in search of an increased glass-forming ability (GFA). The Fe-Si-B ternary system has great potential if it could be additively manufactured via laser bed powder fusion into large, intricate soft magnetic parts for using in highly energy-efficient devices such as motors. However, the GFA of the currently available alloys is low to print fully amorphous parts, making alloy development necessary. Therefore, this study assesses Fe-rich Fe-Si-B alloys in term of eutectic point, which has not been accurately explored over the past four decades. A combination of differential thermal analysis, phase analysis via X-ray diffraction, and microstructural characterization through optical microscopy and scanning electron microscopy in the relevant composition range reveals that the eutectic composition of the Fe-Si-B system with a high Fe content is found to be at or close to Fe 77 Si 11 B 12 at% with a eutectic temperature of 1388 K (1115 °C). Thermal analyses and microstructural studies reveal a sharp melting peak and a well-defined phase transition into the distinct eutectic lamellae, composed of Fe 2 B and α-Fe/Fe 3 Si. Deviations from the eutectic composition either at Si-rich or at B-rich side result in the formation of primary simple dendritic (Fe 3 Si) or faceted dendritic (Fe 2 B) phases, respectively, which precede eutectic solidification. The GFA study using high-energy XRD of the cast plates reveals that the eutectic composition does not necessarily exhibit the maximum critical casting thickness and GFA can be enhanced by strong glass-forming elements in off-eutectic compositions.
Ghavimi et al. (Wed,) studied this question.
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