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 Fe23B6 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.

Effect of Minor Addition of Oxygen on Bulk Metallic Glass Formation of Binary Cu–Zr Alloys via Containerless Processing

“…The details of the experimental setup of the ADL apparatus are similar to those previously reported. [ 20,22 ] The alloy sample was levitated in a conical nozzle by flowing high purity Ar (99.9999%) gas controlled by a mass flowmeter. To adjust the cooling rate of the levitated sample, high‐purity He gas (99.9999%) was used in addition to the Ar gas.…”

“…Furthermore, ADL is an excellent technique for acquiring structural information on high‐temperature materials using high‐flux X‐rays from a synchrotron radiation source. [ 19-22 ] Therefore, in this study, the ADL technique was used to investigate the effect of oxygen on the containerless solidification process of the Cu 47 Zr 53 alloy by observing structure variation using time‐resolved X‐ray diffraction (TRXRD). [ 22 ] Although we investigated the binary Cu–Zr alloys with a Zr concentration of 30–70 at%, the Cu 47 Zr 53 alloy was mainly focused in this article because the alloy of this composition is the best glass former when the oxygen content increased.…”

Re-Examination of the Microstructural Evolution in Undercooled Co-18.5at.%B Eutectic Alloy

“…The ∆T dependencies of the solidification pathways are found to be relatively unequivocal in the Fe-B and Ni-B systems. For example, with an increase in the ∆T, the solidification products change from the stable Fe 2 B phase to the metastable Fe 23 B 6 phase, and then to the metastable Fe 3 B phase [17]. Quirinale et al [18] studied the in situ solidification process, which is dependent on the cooling rate, in electrostatically levitated Fe 83 B 17 alloys, and the results show that the growth of the equilibrium Fe 2 B/α-Fe phases was suppressed, which resulted in the formation of the metastable Fe 23 B 6 phase when the cooling rate was greater than 60 K/s.…”