High temperature reaction of multiple eutectic-component system: The case of solid metallic Zr and molten stainless steel-B4C

The eutectic melting, one of the fundamental phenomena in high temperature reactions involving liquid phases, is a primitive but important subject for both scientific and industrial fields associated with metallurgy. The present study aims at revealing the formation and reaction mechanisms of the multiple eutectic-component system consisting of solid metallic Zr and molten stainless steel-boron carbide (SS-B4C) by combining multiple analytical methods (i.e. powder X-ray diffraction (PXRD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), and dynamic secondary ion mass spectrometry (D-SIMS)) with thermodynamical consideration. The results indicate that the solidified Zr-SS-B4C mixture is composed of major phases of (Fe,Cr)(2)Zr, (Fe,Cr,Ni)(2)Zr, (Ni,Fe)Zr-2, ZrB2, and a minor phase of ZrC. The results also reveal that the eutectic melting between solid metallic Zr and molten SS-B4C can be described as the combination of diffusion kinetics and thermodynamic stability. That is, the initial formation of ZrC and ZrB2 layers at the reaction interface significantly retards the diffusion of other SS-B4C components (i.e. Cr, Fe, and Ni) into solid metallic Zr.