Tian Ni, Jiang Xu, Zhang Yaozhong, Zeng Zijie, Wang Tianshi, Zhao Gang, Qin Gaowu
School of Materials Science & Engineering, Northeastern University, No. 3-11, Wenhua Road, Heping District, Shenyang 110819, China.
Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, No. 3-11, Wenhua Road, Heping District, Shenyang 110819, China.
Materials (Basel). 2022 Aug 28;15(17):5951. doi: 10.3390/ma15175951.
In this study, the strength, elongation, and fatigue properties of 7005 aluminum alloy plates with different configurations of precipitates were investigated by means of tensile tests, fatigue tests, and microstructural observation. We found that the number and size of GP zones in an alloy plate matrix increased and the distribution was more uniform after the aging time was extended from 1 h to 4 h at 120 °C, which led to a rise in both strength and elongation of alloy plates with the extending aging time. The fatigue life of the alloy plates shortened slightly at first, then significantly prolonged, and then shortened again with the aging time extending from 1 h to 192 h and a fatigue stress level of 185 MPa and stress ratio (R) = 0. After aging at 120 °C for 96 h, the precipitates in the alloy plate matrix were almost all metastable η'-phase particles, which had the optimal aging strengthening effect on the alloy matrix, and the degree of mismatch between the α-Al matrix and second-phase particles was the smallest; the fatigue crack initiation and propagation resistances were the largest, leading to the best fatigue performance of alloy plates, and the fatigue life of the aluminum plate was the longest, up to 1.272 × 10 cycles. When the aging time at 120 °C was extended to 192 h, there were a small number of equilibrium η phases in the aluminum plates that were completely incoherent with the matrix and destroyed the continuity of the aluminum matrix, easily causing stress concentration. As a result, the fatigue life of alloy plates was shortened to 9.422 × 10 cycles.
在本研究中，通过拉伸试验、疲劳试验和微观结构观察，研究了具有不同析出相组态的7005铝合金板材的强度、伸长率和疲劳性能。我们发现，在120℃下时效时间从1小时延长至4小时后，合金板材基体中GP区的数量和尺寸增加，且分布更加均匀，这导致合金板材的强度和伸长率均随时效时间的延长而提高。在疲劳应力水平为185MPa且应力比（R）=0的情况下，随着时效时间从1小时延长至192小时，合金板材的疲劳寿命起初略有缩短，然后显著延长，之后又再次缩短。在120℃时效96小时后，合金板材基体中的析出相几乎全为亚稳η'相粒子，其对合金基体具有最佳的时效强化效果，且α-Al基体与第二相粒子之间的错配度最小；疲劳裂纹萌生和扩展阻力最大，导致合金板材的疲劳性能最佳，铝板的疲劳寿命最长，可达1.272×10次循环。当120℃下的时效时间延长至192小时时，铝板中出现少量与基体完全不共格的平衡η相，破坏了铝基体的连续性，容易引起应力集中。结果，合金板材的疲劳寿命缩短至9.422×10次循环。
