Al-Cu-Li合金轧制厚板的疲劳性能及断裂机理研究

李国爱 王俭堂 郝时嘉 陆政 高文理

摘   要：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.

关键词：Al-Cu-Li合金;各向异性;疲劳性能;微观组织

中图分类号：TG146.2                           文献标志码：A

Study on Fatigue Property and Fracture Mechanism

of Al-Cu-Li Alloy Rolled Thick Plate

LI Guoai1，2†，WANG Jiantang3，HAO Shijia1，LU Zheng1，2，GAO Wenli4

（1. AECC Beijing Institute of Aeronautical Materials，Beijing 100095，China;

2. Beijing Engineering Research Center of Advanced Aluminum Alloys and Applications，Beijing 100095，China;

3. Yantai Huaxin Group Co LTD，Yantai 265503，China;

4. College of Materials Science and Engineering，Hunan University，Changsha 410082，China）

Abstract：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.

Key words：Al-Cu-Li alloy;anisotropy;fatigue properties;microstructure

鋁锂合金是一种具有高弹性模量、高比强度、高比刚度、耐腐蚀及焊接性好等诸多优点的轻质铝合金，若用其替代传统的铝合金构件，可以在提高刚度的同时减轻构件10%～20%的重量，因此被广泛应用于军事和航空航天等领域[1-3]. 作为发展较为成熟的第三代Al-Cu-Li合金具有较好的强度和优异的耐损伤、耐腐蚀性能，已取代2124和7050等传统铝合金用于飞机的机翼纵梁、地板横梁、座位导轨和机身隔框等[4]. 这些结构件服役环境复杂（温度变化、应力变化等），承载作用要求材料需具备优异的强度、韧性和抗疲劳性能[5].

国内外学者在铝锂合金疲劳性能方面做了许……