材料期刊网

通过在两相区温度和贝氏体区温度等温处理制备强度达1000MPa、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。

Intercritical annealing and isothermal treatment in bainite region were carried out to obtain the strength 1000MPa and the elongation 234% TRIP steel with low silicon containing aluminum. The fracture mechanism of experimental steel after heat treatment were studied through insitu tensile test and EDX. Experiments show that under tensile stress, the dislocations dislocation move along the slip bands to cause grain boundary dislocations block which caused by stress concentration, while microinitiation holes formed because the adhesive force between ferrite and the surrounding hard phase is relatively weak. With increasing stress, small holes are created, gather, grow and finally become a crack that crossed ferrite grain. When the crack meets the hard phase bainite, it spreads along the edge of the bainite. When a crack meets the retained austenite, concentrated stress around the trip of crack makes retained austenite phase transform to martensite. This is called TRIP effect. The crack changes its direction then goes until fracture. Fracture morphology of the TRIP steel is a dimple pattern with features of plastic fracture.