摘 要5A01铝合金为我国自主研制的不可热处理强化防锈铝合金，在船舶建造领域有广阔的应用前景，目前关于其焊接工艺及焊接接头性能的研究尚报道不多。搅拌摩擦焊是一种全新的固态焊接方法，特别适用于铝合金、镁合金等有色金属的连接。因其变形小、能耗低、无污染等特点，在工业领域得到了广泛的发展。焊接接头残余应力的大小和分布，对焊接结构件在后期服役过程中结构变形、应力腐蚀开裂、疲劳裂纹的扩展等有重要影响。因此研究焊接工艺对5A01搅拌摩擦焊接头组织与性能以及残余应力分布规律有很重要的意义，可以为5A01铝合金更广泛的应用提供理论基础。

    本文对5mm厚的5A01铝合金板进行搅拌摩擦焊对接，试验分为单道搅拌摩擦焊、同向双道搅拌摩擦焊、反向双道搅拌摩擦焊三部分。对搅拌摩擦焊接头进行宏观、微观分析，并讨论不同参数对接头拉伸性能和接头显微硬度的影响规律。试验发现接头横截面为典型“V”型，上宽下窄，并有洋葱环存在；双道焊接可以将焊缝金属搅拌更加均匀，在同向双道焊时抗拉强度明显降低，低于反向双道焊。87012

对5A01铝合金搅拌摩擦焊对接接头残余应力的测试用小孔应力释放法进行，分析结果得，不管是单道焊还是双道焊，其纵向残余应力总是比横向残余应力大；单道焊缝和反向双道焊的纵向残余应力的曲线峰值在焊缝中心处，而同向双道焊缝的纵向残余应力在搅拌区域内出现双峰。

毕业论文关键词 搅拌摩擦焊；5A01铝合金；残余应力；力学性能；

Abstract 5A01 aluminum alloy is high-strength and antirust alloy。 It has broad application prospects in the field of ship building。 The report of research on welding process and property of 5A01 joint is few。 Friction stir welding is a new connection technology in solid phase, especially for aluminum alloy, magnesium alloy, and other non-ferrous metals。 Because of its small deformation, low energy consumption, little pollution, it  has been widely developed in the industrial field。 Residual stress magnitude and distribution of welded structure greatly influence structural deformation, stress corrosion cracking, fatigue crack extension in service。 Thus the study of welding process on the microstructure and performance and residual stress distribution of 5A01 aluminum alloy welded by friction stir welding is very important, applying theoretical basis for its application。

In this paper, 5mm thick 5A01 aluminum alloy plate is connected by friction stir welding。 The experiment is pided into three parts: single-pass welding, two passes in the same direction, two passes in different directions。 The macrostructure and macrostructue of the joints are analyzed。 It is discussed about the effect of different parameters on the tensile strength and hardness of the joints。 It found that the joint’s cross-section is in a typical type of "V" and wider at the top, and onion rings exist。  Metal can be stirred even more when welded with two passes。 Tensile strength of the joint welde by two passes in the same direction is significantly lower than that of the joint welde by two passes in different directions。

Hole-drilling method is used to measure residual stress of the joint of 5A01 aluminum alloy welded by friction stir welding。 It is found that whether the joint is welded by single pass or double passes, longitudinal residual stress is always greater than the transverse residual stress。 In the joints of single pass and double passes in different directions, the curves’ peak values of longitudinal residual stress are both at the center, while there are two peaks in the curve of longitudinal residual stress of the joint of double passes in the same direction。