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利用高功率高重复率的Nd∶YAG激光对6061-T6铝合金钨极弧焊(TIG)焊缝和热影响区进行冲击强化处理,通过调整激光能量、冲击区域,进行了对比试验。通过低循环大应力拉伸疲劳测试获得了未处理和激光冲击强化后的焊接接头试样的安全寿命,分析了激光冲击强化对铝合金焊接接头疲劳性能的影响,根据断口形貌扫描电子显微镜(SEM)和X射线能谱分析(EDS),残余应力和硬度测试结果,研究了激光冲击强化提高焊接接头抗拉疲劳性能的微观机理。结果表明,激光冲击强化使6061-T6铝合金焊接接头安全寿命提高117.1%,其中激光能量为5 J、冲击区域为18 mm×16 mm,双面冲击后接头试样获得最大疲劳寿命。同时激光冲击强化抵消了接头表面残余拉应力并产生残余压应力,显著提高接头硬度,影响深度约1.4 mm。
The high-power and high-repetition rate Nd: YAG laser was used to impact strengthen the TIG weld and heat-affected zone of 6061-T6 aluminum alloy. By adjusting the laser energy and the impact area, comparative experiments were carried out. The fatigue lives of welded joints after untreated and laser shock strengthened were obtained by low cycle and large stress tensile fatigue test. The impact of laser shock on the fatigue properties of aluminum alloy welded joints was analyzed. According to the fracture morphology, the scanning electron microscopy SEM and X-ray energy dispersive spectroscopy (EDS), residual stress and hardness test results. The microscopic mechanism of laser shock strengthening on tensile fatigue properties of welded joints was studied. The results show that the laser shock strengthening enhances the life expectancy of welded joint of 6061-T6 aluminum alloy by 117.1%. The laser energy is 5 J and the impact area is 18 mm × 16 mm. The maximum fatigue life of joint specimen after double-side impact is obtained. At the same time, laser shock intensification counteracts the residual tensile stress on the joint surface and generates residual compressive stress, which significantly increases the joint hardness and affects the depth of about 1.4 mm.