In the present paper, the corrosion fatigue crack initiation and initial propagation mechanism of E690 steel in simulated seawater were studied by stress-controlled fatigue tests and a series of subsequent characterizations on the fracture surface, microstructure and secondary cracks. Results show that the corrosion fatigue crack initiation and initial propagation mechanism evolves with elevated peak stress level in simulated seawater. When peak stress is far below the proof stress, cracks preferentially initiate at the parent austenite grain boundaries (PAGBs) with 68.4% probability and at the ferrite lath boundaries (FLBs) with 31.6% probability. Meanwhile, the cracks also preferentially propagate along the PAGBs and FLBs. Upon the peak stress close to or above the proof stress, cracks turn to initiate from the emerging corrosion pits and propagate without zigzag detour but by splitting the ferrite laths which transversely block its propagation way.

本文通过应力控制疲劳试验研究了E690钢在模拟海水中的腐蚀疲劳裂纹萌生和初始扩展机制，并对断裂表面，微观组织和二次裂纹进行了一系列后续表征。结果表明，在模拟海水中，随着峰值应力水平的升高，腐蚀疲劳裂纹的萌生和初始扩展机制逐渐发展。当峰值应力远低于屈服强度时，裂纹优先以68.4％的概率在母体奥氏体晶界（PAGBs）和31.6％的概率以铁素体板条边界（FLBs）产生裂纹。同时，裂纹也优先沿着PAGB和FLB传播。当峰值应力接近或高于屈服强度时，