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通过在两相区温度和贝氏体区温度等温处理制备强度达1 000 MPa、伸长率为24.3%的含铝低硅TRIP钢,采用扫描电镜进行原位拉伸试验和能谱分析,研究其断裂机制。结果表明,在拉应力作用下,铁素体内部位错沿滑移带运动到晶粒边界引起位错塞积产生应力集中,同时铁素体与周围硬质相之间的结合力相对较弱,由于应力的作用而萌生微孔。微孔在应变应力作用下扩展,贯通,形成裂纹,穿过铁素体。裂纹在扩展过程中遇到硬质相贝氏体时沿其边缘行走。当遇到残余奥氏体时,裂纹前端的应力集中使得残余奥氏体转变为马氏体,产生相变诱发塑性,且因为裂纹前端的应力集中得以释放而钝化,随应力增加裂纹发生扭折,转向扩展,直至断裂。由断口韧窝形貌判断其断裂形式属于塑性断裂。
The aluminum-containing low-silicon TRIP steel with the strength of 1 000 MPa and the elongation of 24.3% was prepared by the isothermal treatment at the two-phase zone temperature and the bainitic zone temperature. The tensile test and energy spectrum analysis were conducted by scanning electron microscope Its fracture mechanism. The results show that the internal dislocations of ferrite move along the slip band to the grain boundary to cause the stress concentration due to the dislocation plugging under the tensile stress, and the binding force between the ferrite and the surrounding hard phase is relatively weak. Due to the role of stress and the initiation of micropores. Micropores expand under strain stress and penetrate to form cracks that pass through the ferrite. The crack travels along its edge as it encounters hard phase bainite during expansion. When the residual austenite is encountered, the stress concentration in the front of the crack causes the retained austenite to transform into martensite, resulting in the phase transition-induced plasticity. Since the stress concentration at the front of the crack is released and passivated, the crack is twisted with the increase of the stress Fold, turn to expand, until broken. The fracture dimples are plastic fractures judged by the morphology of the fracture dimples.