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

• Published in: Optics and laser technology Vol. 119; p. 105668
• Main Authors: Wang, Jiming, Peng, Genchen, Li, Liqun, Si, Changjian, Meng, Shenghao, Gong, Jianfeng
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-11-2019; Elsevier BV
• Subjects: Aluminum alloy thick plate; Aluminum alloys; Aluminum base alloys; Atmospheric pressure; Base metal; Bead on plate welding; Butt joints; Crystal defects; Fiber lasers; Grain size; Laser beam welding; Lasers; Mechanical properties; Microstructure; Penetration depth; Porosity; Pressure effects; Subatmospheric pressure; Tensile strength; Thick plates; Ultra-high laser welding; Weld formation; Welded joints; Subatmospheric pressure; Microstructure; Weld formation; Ultra-high laser welding; Tensile strength; Aluminum alloy thick plate
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2019.105668

•The processing widow of ultra-high laser welding under atmosphere was very narrow.•A qualified 130 mm-thick 5A06 aluminum alloy butt joint was obtained under 10 Pa.•The lowest tensile strength of the joint was up to 95% of the base metal.•The element Mg was the key factor of improving tensile strength rather than grain size.
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 104 Pa was found. When the ambient pressure was below 104 Pa, the weld penetration changed less. Mass of porosities were detected while the ambient pressure was above 102 Pa. When the ambient pressure was below 102 Pa, the porosity in the joints were invisible. Finally, 130 mm 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.