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用拉伸性能相似的三种不同Al-Zn-Mg-Cu合金,研究了显微组织对裂纹扩展的影响。发现在疲劳状态和提高负荷状态,显微组织对裂纹扩展有明显的影响。通过观察断口组织,研究了裂纹扩展的微观机理。用透射电镜(TEM)研究了裂纹尖端前面的塑性区。在所有情况下,透射电镜研究揭示的裂纹扩展机理与断口观察发现的相同。与变形的拉伸试样进行比较,可以评定塑性区内的应力分布情况。该分析表明,在一个很窄的高塑性变形区后面有一个大范围的低变形区。
Three different Al-Zn-Mg-Cu alloys with similar tensile properties were used to investigate the effect of microstructure on crack propagation. It was found that in the fatigue state and increase the load state, the microstructure has a significant effect on the crack propagation. By observing the fracture structure, the microcosmic mechanism of crack propagation was studied. The plastic zone in front of the crack tip was studied by transmission electron microscopy (TEM). In all cases, the crack propagation mechanisms revealed by TEM studies were the same as those observed with fracture observations. Compared with the deformed tensile specimen, the stress distribution in the plastic zone can be evaluated. This analysis shows that there is a wide range of low deformation zones behind a very narrow zone of high plastic deformation.