Comparative study on structural variations during containerless solidification processes of Fe-B and Fe-c eutectic alloys

Abstract

A comparative study on structural variations during the solidification of Fe-C and Fe-B eutectic alloys was conducted by synchrotron x-ray diffraction under containerless cooling conditions using a conical nozzle levitation technique. It was revealed that a metastable phase composed of Fe 23B6 precipitated as the primary crystalline phase from the undercooled liquid Fe83B17 alloy, whereas solidification of the Fe83C17 alloy occurred via a normal phase transformation process according to the Fe-C phase diagram. In addition, decomposition of the metastable Fe23B6 phase to the equilibrium phases shows a dependence on the cooling rate of the sample. By comparing the primary crystalline phase in the Fe83C17 and Fe83B17 alloys, we suggest that the formability of the metastable Cr23C6-type structure is closely related to the glass-forming ability of Fe-metalloid binary alloys. © 2012 ISIJ.