中炭素鋼におけるセメンタイト球状化挙動の電子顕微鏡によるその場観察

概要

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The spheroidization treatment for medium carbon steels has been usually performed by annealing just above A_1 temperature and slow cooling. In this study, the spheroidization behavior of cementites in the steel was in-situ observed by ultra-high voltage electron microscopy, in order to investigate the effect of initial microstructure on the spheroidization behavior. Two microstructures, i. e. fine ferrite-pearlite and bainite, were selected as the initial microstructure for the treatment, and were prepared by thermo-mechanical treatments. By continuous observation, following results were obtained. Re-austenitization occured at colony and grain boundaries in ferrite-pearlite structure. In the case of bainite, it occured in the vicinity of small cementite particle which distributed homogeneously in ferrite grain. Furthermore, substructures were formed by re-arrangement of dislocations. During cooling, coalescence of austenite grains occured. Based upon the observation of this behavior, discussion was focused on the role of internal stress caused by eigen strain due to transformation.
社団法人日本鉄鋼協会の論文
1992-03-01