7475-T7351铝合金抗疲劳性能研究

Fatigue Damage Resistance Characteristics of 7475-T7351 Aluminum Alloy

采用旋转弯曲疲劳试验、轴向加载疲劳试验、疲劳裂纹扩展速率试验等疲劳性能测试方法,研究了7475-T7351铝合金厚板的疲劳性能,并通过透射电镜(TEM)和扫描电镜(SEM)分析了该合金的显微组织和疲劳断口形貌。结果表明:7475-T7351铝合金具有良好的耐疲劳损伤性能,光滑试样(Kt=1)在室温旋转弯曲和高温轴向加载条件下的疲劳极限分别为180.0和345.0MPa,缺口试样(Kt=2.2)在室温旋转弯曲加载条件下的疲劳极限为91.9MPa;合金厚板材料在高温下缺口敏感性有所降低;国产材料裂纹扩展速率随应力比增加而增大,裂纹扩展门槛值减小;国产7475铝合金与进口材料在裂纹稳定扩展阶段裂纹扩展行为基本相当;在近门槛值附近不同应力比下的裂纹扩展门槛值略有差别。

The fatigue damage resistance characteristics of 7475-T7351 aluminum alloy were studied by rotating bar bending fatigue test, axial load test and fatigue crack growth rate test. TEM and SEM were applied to analyze the microstructure and fracture appearance. The resuhs showed that 7475-T7351 aluminum alloy had the excellent fatigue damage tolerance. The fatigue strengths of the alloy for smooth specimens （Kt = 1 ） were 180.0 and 345.0 MPa in room temperature rotating bar bending fatigue test and high temperature axial load test respectively, and the fatigue strength of notched specimens （ Kt = 2.2 ） was 91.9 MPa on room temperature rotating bar bending fatigue test. The fatigue notch sensibility greatly reduced at high temperature. The fatigue crack growth rate increased as the stress ratio enhancing, and the crack growth threshold （△Kth） decreased. The fatigue crack propagation of synthesized and imported 7475 aluminum alloy were almost the same as expected at the fatigue crack growth （△Kth）.