Characterizations of welding mode transformation process during 1-μm and 10-μm laser welding

To reveal the enhancing energy coupling effect of plasma, a comparison of the welding mode transformation process during 1-mu m and 10-mu m laser welding of aluminum alloys is carried out through experimental observation and theoretical analysis. The heat conduction welding stage hardly exists in 10-mu m laser welding and obviously exists in 1-mu m laser welding. Alloy composition and surface roughness of the welded plate hardly influence the deep penetration welding threshold (DPWT) of the 10-mu m laser, whereas they have a significant impact on that of the 1-mu m laser. In addition, 1-mu m laser welding and 10-mu m laser welding have similar DPWTs. These phenomena are attributed to the formation of plasma near the workpiece surface during 10-mu m laser welding owing to metal vapor breakdown by 10-mu m laser irradiation. The plasma remarkably enhances the energy coupling between the 10-mu m laser and workpiece by thermal conduction, and the DPWT of the 10-mu m laser is thus reduced to approximately equal to that of the 1-mu m laser. (c) 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).