Al-Cu-Li合金轧制厚板的疲劳性能及断裂机理研究

Study on Fatigue Property and Fracture Mechanism of Al-Cu-Li Alloy Rolled Thick Plate

利用疲劳试验机、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等设备研究了95 mm厚的Al-Cu-Li合金热轧板材不同方向的组织特征、疲劳性能和断裂机理.结果表明:Al-Cu-Li合金热轧厚板的力学性能和疲劳性能均存在各向异性.LT向(横向)的力学性能和疲劳性能均优于L向(纵向)和ST向(高向),L向(纵向)的力学性能较ST向更好,但疲劳性能较ST向更差.Al-Cu-Li合金厚板的疲劳裂纹源主要出现在试样表面、近表面的夹杂物和晶界处.裂纹扩展过程中,LT向裂纹扩展路径较L向更曲折,ST向具有典型的解理特征,瞬断区形貌与静态拉伸断口相似.晶界越多,裂纹扩展阻力越大,LT向和ST向的未溶第二相能够有效阻碍裂纹扩展,导致其疲劳性能优于L向.

In this paper,the microstructure characteristics,fatigue properties and fracture mechanism of 95 mm Al-Cu-Li alloy hot-rolled thick plates in different orientations were studied by fatigue testing machine,scanning electron microscope(SEM)and transmission electron microscope(TEM).The results showed that the mechanical properties and fatigue properties of Al-Cu-Li alloy hot-rolled thick plate were both anisotropic.The mechanical properties of the L direction are better than those of the ST direction,but the fatigue properties are worse than those of the ST-direction.The fatigue crack sources of Al-Cu-Li alloy thick plates mainly appear on the surface of the sample,near the surface of the inclusions and grain boundaries.During the crack propagation process,the crack propagation path in the LT direction was more tortuous than that in the L direction,and the ST direction had a typical cleavage characteristic.The morphology of the instantaneous fracture zone was similar to that of the tensile fracture.The more grain boundaries,the greater the crack propagation resistance,and the undissolved second phase in the LT direction and ST direction can effectively hinder the crack propagation,resulting in better fatigue performance than that in the L direction.