Metals and Materials International ( IF 3.3 ) Pub Date : 2022-04-21 , DOI: 10.1007/s12540-021-01151-y B. B. He 1, 2 , Q. W. Guan 2
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Dislocation engineering is a novel alloy design strategy to produce advanced high strength steels with both high strength and good ductility, which can be accomplished through an ausforming process. The present work studies the effect of ausforming strain on the evolution of lath martensite microstructure in low carbon steel by detailed transmission electron microscopy observation. Ausforming strain determines the length of the martensite blocks and the substructure in the lath martensite. The large ausforming strain (20%–45%) reduces the martensite blocks and leads to the development of dislocation cell structure, both of which are absent in the ausformed martensite with a small ausforming strain (5%–10%). The formation of the dislocation cell structure in the prior austenite grains after the large plastic deformation inhibits the propagation of martensite and thus reduces the length of martensite blocks. Irrespective of the ausforming strain, the plastic deformation of austenite grains does not lead to an obvious change of martensite lath width. The large ausforming strain slightly enhances the auto-tempering of martensite on the aspect of precipitates density. The coarse precipitates formed close to the lath boundaries after small ausforming strain of 5% is absent in the martensite with large ausforming strain (20%–45%), which is ascribed to the presence of intensive dislocations generated by elevated ausforming strain can facilitate the pipe diffusion of carbon. The present finding serves as the microstructural basis for the application of the dislocation engineering concept in the design of advanced high-strength steel with the martensite as the intrinsic component.
Graphical abstract
中文翻译：
Ausforming应变对低碳钢板条马氏体组织演变的影响
位错工程是一种新颖的合金设计策略，用于生产兼具高强度和良好延展性的先进高强度钢，可通过奥氏成形工艺完成。本工作通过详细的透射电子显微镜观察研究了奥氏变形应变对低碳钢中板条马氏体组织演变的影响。Ausforming 应变决定了马氏体块的长度和板条马氏体中的亚结构。大的变形应变（20%~45%）减少了马氏体块并导致位错晶胞结构的发展，而这两者在具有小变形应变（5%~10%）的变形马氏体中都不存在。大塑性变形后原奥氏体晶粒中位错胞组织的形成抑制了马氏体的扩展，从而减少了马氏体块的长度。不考虑奥氏体变形应变，奥氏体晶粒的塑性变形不会导致马氏体板条宽度发生明显变化。大的奥氏变形应变略微增强了马氏体在析出物密度方面的自回火。5% 的小奥氏变形应变后在板条边界附近形成的粗大沉淀物在具有大奥氏变形应变 (20%~45%) 的马氏体中不存在，这归因于由升高的奥氏变形应变产生的密集位错的存在可以促进碳的管道扩散。
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