Study On The Technology And Property Of Joint For Laser Welding Of Aluminum Alloys

As a heat source of high energy density,Laser has particular advantages,such as high welding speed,small welding deformation,the narrow fusion width and heat-affected zone ; however,due to the low melting point of aluminum alloy ,the high reflectivity for the laser,the laser welded joints exist some weld defects. For example, the weld surface may be caved,produce crack or porosity. As a new and advanced welding technology,YAG laser - MIG arc hybrid welding has a good adaptation of the ZL114A aluminum alloy; the welding of aluminum alloy can be processed in the lower laser power. The electricity arc can reduce or weaken the disadvantage of the plasma,which caused by simplex laser welding. The interaction of the two sources of heat changed distribution of the power density on time and space,increased the laser absorption rate of the workpiece,increased the welding deepness. That can improve the stability and reliability of the welding a certain extent.YAG-MIG hybrid welding technology not only using the advantages of two heat source, but also making up the shortcoming of them,it is an new and efficient heat source.Researched the technology and relation theory of YAG laser - MIG arc hybrid welding based on the material of ZL114A aluminum alloy. Focus on the microstructure composition distribution and mechanical properties of the welding joints and their relationship based on the research and the optimize of the weld technics in the effect of both thermal resource. Analyzed the macroscopical shape,microstructures,composition distribution,microelement content,appearance of the break zone,mechanical properties and micro hardness of welded joint,through the technology of metallographic analysis,ESEM / FSEM / SEM,the tensile strength test and micro hardness test. The results showed that the YAG-MIG hybrid welding has a good feasibility for ZL114A alloy. Due to the complementary role of the laser and arc,The high quality joint can be achieved in a high welding speed when the welding parameter is appropriate,the mechanics properties of the welding joint was up to 80 percent of the base metal. Welding nuclear zone is the minimum hardness area,and the hardness distributed symmetrical and uniform,The hardness gradually increased when away from the welding line,and reduced once again when arrive at the transition area,after there gradually increase to the hardness of the base metal; The crystallizing morphology of the welding joint was equiaxed grains in the center and coarse columnar crystals in the heat affected zone. The fusion zone and the heat-affected zone existed large microstructure. The result of tensile properties shows that the fractographs of the tensile specimens has not showed the obvious plastic flow,the fracture characteristic is belong to brittle fracture,the break position is generally in the heat affected zone(HAZ) and the fusion zone(FZ),where had large Microstructure,corresponding to the softening zone of the micro-hardness and the zone where elements content fluctuated most in the elements Figure.Discussed the relationship of the microstructures,mechanical properties with the laser power,wire feed speed(WFS),welding speed,MIG welding line energy .It was found that under certain welding condition the weld depth mainly depends on the laser power and the width depends on the arc power,Therefore,in pairs,in the process of welding backing welding,Using high-energy density laser (Power 4.0kw) as the main sources of heat,and the use of the lower energy electric arc as supplemented ,By this way ensure that the 3 mm blunt edge completely melted,getting more welding depth as far as possible,The second welding line,as for the characteristics of the U-shaped groove,adopted the combination heat of higher arc energy and lower laser power (2.0 kw),It finally got a good weld,this also confirmed the reasonableness of the combination heat.In addition, the microstructure and the element component about the material of the joint of aluminum-magnesium alloy 5A06 welded by laser with wire,also be discussed in this paper; The results showed a small grain microstructure,the main component was theα(Al) +β(Al3Mg2) on the Al-based; Elements evenly distributed in vertical and horizontal,and there is no element accumulate, the base metal is not diluted obviously,So the choice of 5356 wire very reasonable.Finally analyzed the macro-morphology and microstructure about the joints of 11.5 mm and 12 mm of ZL114A which were welded by 8 kw laser.