Abstract The rate of bainite formation depends on several factors such as austenite grain size, decomposition of austenite into other phases and austenite composition. Although studies have been carried out to understand various factors affecting bainite formation, open lines of investigation still remain. In this work, the effect of ferrite formation prior to bainite formation as well as the effect of parent austenite grain boundary composition on the bainite formation kinetics is investigated. With this aim, bainite formation treatments directly after complete austenitization and in combination with an intermediate heat treatment step prior to bainite formation were applied to a low-carbon silicon-containing steel. The intermediate heat treatment step leads to ferrite formation at and/or elemental segregation to austenite grain boundaries which were characterized using scanning electron microscopy, electron backscatter diffraction analysis and atom probe tomography. The results indicate that the kinetics of bainite formation can be accelerated with the help of an intermediate heat treatment step prior to bainite formation. The acceleration of bainite formation is mainly due to increase in the density of bainite nucleation sites.

中文翻译：

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奥氏体晶界和铁素体形核对钢中贝氏体形成的影响

摘要 贝氏体的形成速率取决于奥氏体晶粒尺寸、奥氏体分解成其他相和奥氏体成分等多种因素。尽管已经进行了研究以了解影响贝氏体形成的各种因素，但仍然存在开放的调查路线。在这项工作中，研究了贝氏体形成之前铁素体形成的影响以及母体奥氏体晶界成分对贝氏体形成动力学的影响。为此，在完全奥氏体化之后直接进行贝氏体形成处理，并结合贝氏体形成之前的中间热处理步骤，将贝氏体形成处理应用于低碳含硅钢。中间热处理步骤导致在奥氏体晶界处形成铁素体和/或元素偏析到奥氏体晶界，使用扫描电子显微镜、电子背散射衍射分析和原子探针断层扫描对其进行表征。结果表明，在贝氏体形成之前，借助中间热处理步骤可以加速贝氏体形成的动力学。贝氏体形成的加速主要是由于贝氏体形核位点密度的增加。