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通过采用扫描电镜及透射电镜等手段,观察并研究了TWIP钢在低周单轴循环对称拉压载荷下的疲劳断裂后的显微组织。结果表明:TWIP钢矩形试样的疲劳裂纹一般萌生于角部,从表面萌生时可能表现为多个疲劳源。在低周疲劳变形过程中,TWIP钢不但产生了形变孪晶,还产生了大量的微条带,其实质为细微孪晶片层和驻留滑移带。疲劳裂纹主要萌生于微条带对晶界和孪晶界的撞击引发的孔洞。孔洞串连接起来成为裂纹,夹杂物促进了裂纹扩展。随着裂纹的扩展,试样的承载面积不断减小,最终发生快速的韧性断裂。
Through the use of scanning electron microscopy and transmission electron microscopy and other means, observed and studied the TWIP steel in the low-cycle uniaxial cyclic tension and compression load after fatigue fracture microstructure. The results show that the fatigue cracks of rectangular specimens of TWIP steel usually occur at the corner and may appear as multiple fatigue sources when the surface is initiated. During low cycle fatigue deformation, TWIP steel not only produced deformation twins, but also produced a large number of micro-strips, which are essentially fine twins and resident slip bands. Fatigue cracks mainly occur in the holes caused by impact of micro-strips on grain boundaries and twin boundaries. Hole strings connect to become cracks, and inclusions promote crack propagation. As the crack propagates, the bearing area of the sample decreases and eventually the rapid ductile fracture occurs.