高强度无取向电工钢疲劳性能及断裂机制

测试了高强无取向电工钢的S-N曲线,并借助光学显微镜、扫描电子显微镜、透射电子显微镜分析了实验钢组织,疲劳断口形貌和位错结构.结果 表明:室温条件下,频率为20 Hz,应力比R为0.1,循环107周次时,实验钢的疲劳强度为360 MPa,疲劳裂纹萌生于实验钢的次表面,裂纹萌生点附近有沿晶开裂现象,疲劳裂纹扩展区域有解理台阶与疲劳条纹,瞬间断裂区是韧性断裂,有大量韧窝.实验钢在循环应力作用下基体中产生了大量位错,并有驻留滑移带终止在晶界位置.

Fatigue properties and fracture mechanism of high strength non oriented electrical steel

The S-N curve of a high strength non-oriented electrical steel was tested. The microstructure and fatigue fracture morphology and dislocation were analyzed by optical microscope, scanning electron microscope, transmission electron microscope. The results showed that: at room temperature and the frequency of 20 Hz and the stress ratio R of 0.1, the fatigue strength of the experimental steel was 360 MPa when the cycle was 10⁷  cycles. The fatigue crack initiation at the surface of the steel and the intergranular fracture phenomenon occurred. There were cleavage steps and fatigue stripes in the fatigue crack propagation region, and the instantaneous fracture region was ductile fracture with a large number of dimples. A large number of dislocations appeared in the matrix under cyclic stress, and there persistant slip band terminated at the grain boundary position.