In-Situ Observation of Growth Behavior of Niobium Carbide during Dual-Phase Rapid Solidification of SUS347H

In order to improve solidification cracking susceptibility, the crystallization of a heterophase such as the niobium carbide in the brittle temperature range is one of the effective techniques. In such a system, not only the growth behavior of dendrites during the rapid cooling but also the crystallization behavior of heterophase is very important. Therefore, diffraction patterns of a dual-phase mode Nb-bearing stainless steel during rapid cooling were investigated by in-situ two-dimensional time-resolved X-ray diffraction for the first time in order to reveal the microstructure formation. We discuss the growth behavior of dendrites with crystallization of niobium carbides. Subsequently, the niobium carbide formed epitaxially to the dendrite of the preferred in-plane orientation, having a small distorted orientation. With undercooling of several degree Celsius, the coherent growth on the δ -ferrite was stable for niobium carbide.