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本文采用S—N曲线和疲劳裂纹扩展试验两种方法研究了三种Al-Mg-Si合金在峰值时效状态下的疲劳特性。这三种合金均无粗大的含铁的金属间化合物,它们的屈服应力与晶粒尺寸都相近,其循环—应力应变曲线也相似。其中,一种合金基本上是纯三元合金,另两种合金由于添加了锰而含有其体积百分数分别为0.22和0.61,其直径为0.1微米的金属间化合物弥散相质点。与先前对这一领域的研究有所不同的是发现在很宽的△K值范围内,弥散相质点降低裂纹扩展速率,而且在低△K值下,弥散相质点也影响到断裂通路由晶间型向穿晶型的转变。这种结果可以解释为由于弥散相质点存在的缘故,因为位错与这些质点的相互作用引起滑移带间距变小,从而使滑移的分布均匀,这就降低了裂纹尖端塑性区内滑移带前的应变集中。
In this paper, the fatigue behavior of three Al-Mg-Si alloys under peak aging condition was studied by means of S-N curve and fatigue crack growth test. All three alloys have no coarse iron-containing intermetallic compounds. Their yield stress and grain size are similar, and their cyclic-stress-strain curves are similar. One of the alloys is essentially a pure ternary alloy, and the other two alloys contain, due to the addition of manganese, interstitial particles of intermetallic compounds having a volume fraction of 0.22 and 0.61, respectively, and a diameter of 0.1 μm. In contrast to the previous studies in this field, it was found that within a wide range of ΔK values, the dispersed phase particles reduce the rate of crack propagation, and at low ΔK values, the particles of the dispersed phase also affect the fracture path Interplanetary to transcrystalline transition. This result can be explained by the presence of dispersed phase particles because the slip band spacing decreases due to the interaction of dislocations with these particles, resulting in uniform slip distribution, which reduces the slip in the plastic zone of the crack tip With the strain before the focus.