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通过拉伸性能和疲劳裂纹扩展试验研究Al-Zn-Mg-Cu合金的拉伸性能和疲劳性能。拉伸试验结果显示,与利用峰时效温度的传统回归再时效(RRA)相比,较低时效温度的RRA处理能够提高合金的伸长率,但是降低了合金的强度。但是,在前面改良的RRA处理基础上,在再时效之前增加自然时效,可以同时提高合金的强度和塑性。疲劳测试结果显示,两条改良的工艺路线都可以降低疲劳裂纹扩展速率。尤其是采用较低再时效温度改良的RRA工艺获得最低的疲劳扩展速率。自然时效处理提高了GP区的形核速率。大量的GP区都能够被位错切割。因此该状态合金拥有最高的强度和伸长率,以及较低的疲劳裂纹扩展速率。
Tensile properties and fatigue properties of Al-Zn-Mg-Cu alloys were investigated by tensile test and fatigue crack growth test. The tensile test results show that the RRA treatment with lower aging temperature can improve the elongation of the alloy but reduce the strength of the alloy compared with the conventional regression re-aging (RRA) using the peak aging temperature. However, based on the previously improved RRA treatment, natural aging is added before re-aging to simultaneously increase the strength and ductility of the alloy. Fatigue test results show that two modified routes can reduce the fatigue crack growth rate. In particular, the lowest fatigue expansion rate is achieved with the RRA process with a lower re-aging temperature. Natural aging increases the rate of nucleation in the GP zone. A large number of GP zones can be dislocated. The state alloy therefore has the highest strength and elongation, as well as a lower fatigue crack growth rate.