铝合金激光焊与复合焊焊缝气孔形成机理研究

Study on Formation Mechanism of Weld Porosities in Aluminum Alloy Jointed by Laser and Laser Hybrid Welding

利用金相显微镜、扫描电镜观察6009-T6铝合金激光焊和激光-电弧复合焊焊缝中气孔的分布情况及形貌,结合焊缝气孔内壁EDS点扫描分析,并通过图形计算软件计算出焊缝区气孔率。结果表明,相比激光焊,激光-电弧复合焊焊缝中的气孔大小及气孔率显著降低;激光焊焊缝中气孔比较大、形状不规则,而复合焊气孔是比较小的椭球形;进一步分析表明,激光焊主要以工艺类气孔为主,其根本原因是匙孔的失稳;激光-电弧复合焊接以冶金类气孔为主,主要与氢在熔池的析出和氧化物的存在有关;激光焊焊缝气孔内的Mg含量高于焊缝区,而激光-电弧复合焊时焊缝气孔内的Mg含量和焊缝区几乎一样。

Distribution and morphology of the weld porosities in 6009-T6 aluminum welded by laser and laser hybrid welding were investigated by metallographic microscope and scanning electron microscope（SEM）.Porosity in weld zone was calculated through graphic calculation software and EDS point scanning analysis in the inwall of weld porosity.The results showed that the size and rate of porosity in laser hybrid weld were significantly reduced compared to the laser weld.Weld porosities in laser weld were a little big and irregularly shaped,when they were small ellipsoid distributed in laser hybrid weld.Moreover,on account of the instability of keyhole,porosities in laser weld were mainly process ones;porosities in laser hybrid weld were mainly metallurgical ones that was closely related to the precipitations from molten pool and the existence of oxides.Also,Mg content in laser weld porosity was higher than weld zone,while Mg content in laser hybrid weld porosity and weld zone were nearly the same.