Abstract The evolution of the substructure and the distribution of interstitial elements in lath martensite during tempering in soft martensitic stainless steel X4CrNiMo16-5-1 was studied with line profile analysis of diffractograms from energy dispersive synchrotron X-ray diffraction, local chemical analysis with atom probe tomography and orientation mapping with electron backscatter and transmission Kikuchi diffraction. Martensite formation occurred below 135 °C without auto-tempering and led to a dislocation density in martensite of 3.8 ∙ 1015 m−2, as determined from X-ray line profile analysis. On tempering, carbon and nitrogen segregated to low-angle and high-angle grain boundaries. Recovery commenced above 550 °C and led to a reduction in dislocation density to a steady value of 4 ∙ 1014 m−2 from 600 to 750 °C. Further tempering led to a second increase in dislocation density at room temperature, owing to the transformation of reverted austenite, formed above 650 °C, into martensite on cooling. It was observed that the recovery of martensite competes with the formation of reverted austenite. The interpretation of the coherently diffracting domain size obtained from X-ray line profile analysis was critically discussed in the context of the internal structure in martensite.

中文翻译：

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低间隙马氏体不锈钢回火过程中亚结构的演变

摘要 利用能量色散同步辐射X射线衍射谱线谱分析和原子探针局域化学分析，研究了软质马氏体不锈钢X4CrNiMo16-5-1回火过程中板条马氏体亚结构的演变和间隙元素分布。电子背散射和透射菊池衍射的断层扫描和方向映射。马氏体形成发生在 135 °C 以下，没有自动回火，并导致马氏体中的位错密度为 3.8 ∙ 1015 m-2，根据 X 射线线轮廓分析确定。回火时，碳和氮偏析到低角度和高角度晶界。恢复在 550 °C 以上开始，并导致位错密度从 600 到 750 °C 降低到 4 ∙ 1014 m-2 的稳定值。由于在 650 °C 以上形成的回火奥氏体在冷却时转变为马氏体，因此进一步回火导致位错密度在室温下再次增加。观察到马氏体的恢复与回复奥氏体的形成竞争。在马氏体内部结构的背景下，批判性地讨论了从 X 射线线轮廓分析获得的相干衍射域尺寸的解释。