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Behaviour of dendrites in steels under welding conditions of a practical manufacturing process were investigated using the TRXRD method for in-situ weld observation with the uniquely-sensitive two-dimensional pixel detector. Consequently, the crystal growth during the rapid cooling was caught in detail and employed a systematic peak profile analysis in order to acquire the essential information for controlling the weld microstructure. Our results would suggest the microstructure formation process of low alloy in directional solidification during rapid cooling. Simultaneously, we discuss the possibility of detecting the nucleation. Further, in order to improve the solidification cracking susceptibility, the crystallization of hetero-phase like the niobium carbide in the brittle temperature range (BTR) is one of effective techniques. In such a system, not only the growth behavior of dendrites during the rapid cooling but also the crystallization behavior of hetero-phase 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 degrees C, the coherent growth on the ä-ferrite was stable for niobium carbide. |
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