热输入对6A02铝合金光纤激光焊缝成形的影响

采用大功率密度的光纤激光对1.0 mm厚的6A02铝合金进行了激光焊接，着重研究了焊接热输入对焊缝宏观形貌、组织和性能的影响. 结果表明，采用高速焊接且热输入控制在8～22 J/mm范围内可以获得稳定全熔透焊缝. 典型的光纤激光焊缝横截面常呈近X形，此种形貌的焊接温度场不均匀性较小，有利于减少焊接失稳和变形. 从熔合线至焊缝中心，显微组织逐渐从柱状晶组织向混合组织(柱状晶+等轴晶)转变. 随焊接热输入的降低，焊缝区的显微组织相对细化，接头熔合线附近的软化现象逐渐减弱，焊缝区显微硬度和接头抗拉强度均略有增加.

Effect of heat input on weld appearance for fiber laser welding 6A02 aluminum alloy

The fiber laser beam with high power density is used for welding 6A02 aluminum alloy with 1.0mm thickness. And the effects of heat input on weld macrography, structure and properties are studied. The results show that the stable fully penetration weld could be obtained when the heat input is controlled in the range of 8-12 J/mm and the welding speed is very high. The typical cross section of the welds always presents near X shape. The characteristic of the welds could reduce the nonuniformity of welding temperature field. It also could reduce welding buckling and deformation. The columnar microstructure is formed near the fusion line. The mixed microstructures, including columnar grains and equiaxed grains, distribute in the center of the weld. The transition from columnar microstructure to mixed microstructures can be found from the fusion line to the weld center. With the heat input reduced, the microstructures of the weld zone are tendency to fine, the soften phenomenon near the fusion line is helpful to weak, the microhardness of the weld zone and the tensile strength of the joints are increasing slightly.