Comparative Study on Structural Variations during Containerless Solidification Processes of Fe-B and Fe-C Eutectic Alloys

摘要

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_(23)B_6 precipitated as the primary crystalline phase from the undercooled liquid Fe_(83)B_(17) alloy, whereas solidification of the Fe_(83)C_(17) alloy occurred via a normal phase transformation process according to the Fe-C phase diagram. In addition, decomposition of the metastable Fe_(23)B_6 phase to the equilibrium phases shows a dependence on the cooling rate of the sample. By comparing the primary crystalline phase in the Fe_(83)C_(17) and Fe_(83)B(17) alloys, we suggest that the formability of the metastable Cr_(23)C_6-type structure is closely related to the glass-forming ability of Fe-metalloid binary alloys.