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将两种碳素结构钢(15,45)和Cr25Ni20不锈钢的试样在扫描电镜中进行拉伸试验,并对它们的延性断裂的微观过程进行了动态观察。结果表明,裂纹总是优先在夹杂物与金属基体的界面上,孪晶与基体之间的界面上以及σ相与基体之间的界面上成核。前二者的裂纹沿界面传播、钝化并沿拉伸方向变宽;对于后者来说,裂纹成核后,在σ相内解理扩展。最后,裂纹沿切变方向彼此连接并导致断裂。
Two types of carbon structural steel (15,45) and Cr25Ni20 stainless steel samples were subjected to tensile test in a scanning electron microscope, and the microscopic process of their ductile fracture was dynamically observed. The results show that the crack always preferentially nucleates at the interface between inclusions and metal matrix, the interface between twins and matrix, and the interface between σ phase and matrix. The former two crack propagation along the interface, passivation and widening along the direction of stretching; for the latter, the crack nucleation, crack propagation in the σ phase. Finally, the cracks are connected to each other in the shear direction and cause cracks.