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借助扫描电镜(SEM)装载的原位拉伸台,观察了经热处理的两种改性高锰钢裂纹萌生与扩展的动态变化过程。结果表明,在改性高锰钢原位拉伸过程中,裂纹源主要为预制缺口处、滑移线密集处、第二相/奥氏体界面及晶界。载荷使奥氏体基体内部形成高密度滑移线,裂纹扩展以向晶内滑移线密集处扩展为主,碳化物/奥氏体界面次之。对于含C和Mn较高的改性高锰钢Mn18,当塑性变形达到一定程度后,由于位错塞积和晶界阻碍效应,碳化物与基体的协同运动受到阻碍,在较大颗粒状碳化物/奥氏体界面产生应力集中,裂纹由此扩展而发生断裂。
The dynamic change of crack initiation and propagation of the two modified high manganese steels treated by heat treatment was observed by means of the in-situ tensile stage loaded by scanning electron microscope (SEM). The results show that in the process of in-situ tensile modification of high manganese steel, the crack sources are mainly prefabricated notch, slip line dense area, second phase / austenite interface and grain boundary. The load causes the high-density slip line to form inside the austenite matrix, and the crack propagates to expand mainly in the intracrystalline slip line, and the carbide / austenite interface takes the second place. For Mn18 with higher C and Mn, when the plastic deformation reaches a certain level, the synergistic movement between carbide and matrix is hindered due to the dislocation plugging effect and the grain boundary obstruction effect. In the case of larger granular carbonization Material / austenite interface stress concentration, the crack thus extended and fracture.