TIG与FSW焊接工艺下2219铝合金疲劳裂纹扩展性能研究

目的 研究钨极惰性气体保护焊（TIG）和搅拌摩擦焊（FSW）对2219铝合金焊接接头疲劳性能的影响，并探究这2种不同焊接技术条件下焊接接头疲劳裂纹的产生与裂纹扩展原理，了解2种焊接接头的抗裂纹扩展能力，为工程实践应用提供数据参考。方法 采用疲劳裂纹扩展试验方法，测试上述2种焊接工艺条件下焊缝金属和热影响区组织的疲劳裂纹扩展速率da/d N和阈值，使用光学显微镜和扫描电子显微镜观察并分析金相组织和疲劳断口形貌特征。结果 疲劳裂纹倾向于沿裂纹处萌生，裂纹的存在成为主要的裂纹扩展源头，有利于加速裂纹向前延伸。热影响区由于组织结构不均匀，不同位置的晶粒尺寸存在明显差异，疲劳裂纹扩展路径倾向于沿靠近焊缝一侧向靠近母材区域扩展。TIG焊接工艺下焊缝金属和热影响区的裂纹扩展速率明显低于FSW焊接工艺下的焊缝金属和热影响区，与此同时，TIG焊接接头表现出优良的抗疲劳裂纹扩展性能。结论 通过此研究，建议2219铝合金焊接接头采用TIG焊接工艺，抗疲劳裂纹扩展效果更佳。

Fatigue Crack Growth Property of 2219 Aluminum Alloy under TIG and FSW Welding Process

The work aims to study the effects of tungsten inert gas welding (TIG) and friction stir welding (FSW) on the fatigue properties of 2219 aluminum alloy welded joints, explore the principle of fatigue crack generation and crack growth of welded joints under these two different welding conditions, and understand the anti-crack growth ability of the two welded joints, so as to provide data reference for engineering practice. The fatigue crack growth rate da/dN and threshold value of the weld metal and heat affected zone under the two welding methods were tested by fatigue crack growth test. The metallographic structure and fatigue fracture morphology were observed and analyzed by optical microscope and scanning electron microscope. Fatigue cracks tended to initiate along the crack. The existence of cracks became the main source of crack growth, which was conducive to accelerating the forward extension of cracks. Due to the uneven structure of the heat affected zone, the grain size at different positions was obviously different and the fatigue crack growth path tended to expand from the side near the weld to the area near the base metal. The crack growth rate of weld metal and heat affected zone in TIG welding process was significantly lower than that in FSW welding process. Meanwhile, the TIG welded joints showed excellent anti-fatigue crack growth property. Through this study, it is recommended that 2219 aluminum alloy welded joints should be treated by TIG welding process, which will obtain better anti-fatigue crack growth effect.