30 kW-level laser welding characteristics of 5A06 aluminum alloy thick plate under subatmospheric pressure

摘要

In order to explore ultra-high fiber laser welding characteristics of 5A06 aluminum alloy, bead-on-plate welding was performed under atmospheric and subatmospheric pressure with the maximum laser power of 30 kW. The results showed that it was very difficult to carry out a defect-free weld joint with a satisfactory penetration depth under atmospheric pressure. Then, the effects of ambient pressure and defocus distance on weld appearance and penetration depth were investigated. The optimum process window of ultra-high laser power was found. Moreover, the existence of a critical ambient pressure of 10(4) Pa was found. When the ambient pressure was below 10(4 )Pa, the weld penetration changed less. Mass of porosities were detected while the ambient pressure was above 10(2) Pa. When the ambient pressure was below 10(2) Pa, the porosity in the joints were invisible. Finally, 130 nun thick 5A06 aluminum alloy butt joint without defects was obtained from both sides of the plate in only two passes. The relationship between mechanical properties, microstructure and element Mg distribution was revealed. Tensile strength in the overlap zone was the highest and the fracture occurred at the base metal, while other zones were at the weld bead. Microstructure observations and EDS tests showed that the content of element Mg made a greater contribution to the tensile strength of the joint than grain size.