<I>In-Situ</I> Observation for Weld Solidification in Stainless Steels Using Time-Resolved X-ray Diffraction

Abstract

Characterizing of directional solidification mode of Fe-Cr-Ni alloys during welding was performed using intense synchrotron radiation probe. Consequently, the crystal growth in the rapid solidification process was revealed in detail and the peak profile was systematically analyzed in order to acquire the essential information for controlling the weld microstructure. Then, the crystallization timing of the primary and secondary phases was discussed. Furthermore, the possibility of the lattice rotation to commensurate (i) each dendrite and (ii) crystallites in the dendrites is suggested.

Two-Dimensional Time-Resolved X-ray Diffraction Study of Directional Solidification in Steels

“…In our previous work, it was expected that the mist-like pattern would be correlated with the nucleus of dendrites in the high alloy. 17) That is, the phenomena in the vicinity of the critical nucleus may be observed on average as weak broad patterns that are scattered by the wide distribution of lattice spacing and atomic distance. Dendrites behaviour in the low alloy would be also similarly expected in the high alloy.…”

“…This is different from the rotation that centers on the direction of dendrite growth suggested by high-alloy steels. 17) Considering geometry, the diffraction spots would blink on the two-dimensional diffraction pattern by rotation of the dendrite. However, the diffraction spot of 220 in the low-alloy is caught as a continuous change from the mist-like pattern to the sharp spot.…”

“…TRXRD experiments provide information about phase transformation as a function of weld time, but do not directly provide information about weld temperatures. In order to relate weld time to weld temperature, the temperature of the weld metal was measured continuously by the thermocouple of type R. 17) We utilized one of the cases that the thermocouple did not react with molten steels and where it contacted enough with molten steels.…”

“…We assumed the rotation of dendrites from the discontinuous diffraction pattern recorded by the imaging plate along onedirection of the reciprocal space. [17][18][19][20][21] Then, the nucleus of dendrites was observed in the mist-like diffraction pattern of the initiate stage in high alloy. Although these experiments have had some success in the observation of a solidification process, the influence of the crystal preferred orientation by eutectic growth was not avoided.…”

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

“…Our group has observed a solidification and a phase transformation process by an in-situ observation technique of the directional solidification, which results in dendrite growth during rapid cooling. [9][10][11][12] In this work, a displacement of diffraction patterns of a dual-phase solidification mode stainless steel with crystallization of niobium carbides during rapid cooling is investigated by in-situ two-dimensional time-resolved X-ray diffraction. Then, we discuss the growth behavior of the dendrite with crystallization of niobium carbides.…”