Study On The Laser Beam Welding Of 6061 Aluminum Alloy

Because of the wide consumption and huge market demand of 6061 aluminum, the research of laser beam welding (LBW) of thin and medium 6061 plates was carried on in this paper. The research experiments includes autogeneous laser welding (ALW) and laser filler welding (LFW) of two kinds of thinckness 6061 aluminum plates-2.5mm and 6mm thick. Based on the observation and analyst of influence factors and conditions of the welding process, parameters get optimized, appearaces and mechanical properties of welding seams are improved; furthermore how the filler influences the laser beam welding process and weldability of joints were studied with the help of tension test, fracture morphology, micro-structure analyses.As results of autogeneous laser weldings shown that the 2.5-thick 6061 plate’s weldability is better than the 6mm-thick plate’s, along with a wider parameters range than 6mm-thick plates-laser power betweent 2000W and 3750W, adopted a poper welding speed between 2m/min-7m/min, a smooth welding seam with fish-scale patterns is easily got. On the contrary, the welded joint of 6mm-thick plate shall be got when the laser power is over 8500W, and its range of welding speed is narrow-4.2m/min-4.8/min. After parameter optimized, the tensile strength of 2.5mm-thick welded joints is higher than the base metal’s, and the 6mm-thick welded plate’s could be 79.6% of the base metal’s.The reults of filler laser weldings showed that the range of filler feeding speed of the 2.5-thick aluminum plate is as well as wider than the 6mm-thick plate’s. During FLW of 2.5mm-thick plates, when laser power 2000W, welding speed 2m/min, in the range of filler feeding speed 0-9m/min, a smooth welding seam with fish-scale patterns is easily got. On the contrary, when laser power 9500W, welding speed 4.8m/min, in the range of feeding speed 8-llm/min,6mm-thick welded joints are barely formed. After parameter optimized, the tensile strength of 2.5mm-thick welded joints is higher than the base metal’s, too, and the 6mm-thick welded plate’s could be 70.4% of the base metal’s.The results of analysis using microscope indicated that the welded joint is made up with Mg2Si and a(Al) matrix, there exist columnar crystals in fusion zone, dendrite and equiaxed crystals in weld metal; the size of columnar crystals of 2.5mm samples is small, and found no porosity in the joint, the more porosity, the more thickness of the samples.Micro-hardness tests showed that the hardness of the welding zones in aluminum alloy specimens of laser welding and laser welding with filler wire are lower than the base metal, which is called as weld "softening" phenomenon.