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用透射电镜对超高强度钢喷丸和挤压强化层中的精细组织、疲劳裂纹尖端塑性区内的位错结构、微观组织和裂纹扩展行为问的联系进行了研究。结果表明,不同试验条件所产生的拉应力和周期应力均可引起显微组织中残余奥氏体的应变相变和位错胞状组织。喷丸所产生的周期应力可导致下贝氏体内ε-碳化物的退化和显微组织中的亚晶。在塑性区内存在高位错密度的主位错带。就马氏体板条晶而论,裂纹扩展多为穿品,裂纹扩展遇到束界时方向发生较大变化。
The relationship between the microstructure and the dislocation structure, the microstructure and the crack growth behavior in the plastic zone at the tip of the fatigue crack was investigated by transmission electron microscopy. The results show that tensile stress and periodic stress produced by different test conditions can induce the strain transformation and dislocation cell structure of retained austenite in the microstructure. The periodic stress generated by shot peening can lead to the degradation of ε-carbides in the lower bainite and the sub-crystallites in the microstructure. There are main dislocation belts with high dislocation density in the plastic zone. In terms of martensite slab crystal, the crack propagation is mostly penetrating, and the direction of crack propagation changes greatly when it encounters the beam boundary.