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本文应用金属薄膜试样的透射电子显微镜的分析方法,以及扫描电镜和光学显微镜的分析方法,研究调质状态40Mn钢拉伸加载过程变形度对位错结构和裂纹萌生的影响。条状铁素体和渗碳体试样在拉伸加载过程中随延伸率δ的增加,铁素体中的位错网很快演变为高密度的位错缠结和拉长的位错胞。显微组织特征直接影响裂纹的萌生部位。微孔往往在铁素体与渗碳体的界面处和条状铁素体间的边界处萌生,开裂的早期阶段主要是形成微孔群。
In this paper, the transmission electron microscopy analysis of metal thin film samples and the analysis methods of scanning electron microscopy and optical microscopy were used to study the effect of deformation degree on the dislocation structure and crack initiation during the tensile loading of 40Mn steel. With the increase of elongation δ, the dislocation networks in ferrite rapidly evolve into high-density dislocation-entangled and elongated dislocation cells during the tensile loading of strip-like ferrite and cementite samples . The microstructure features directly affect the initiation of cracks. Micropores tend to germinate at the interface between ferrite and cementite and at the boundary between strip-like ferrite. The early stages of cracking are mainly the formation of micropores.