Copper alloys are widely employed in fields such as electrical engineering and aerospace due to their excellent electrical and thermal conductivity. However, the high reflectivity and thermal conductivity of copper pose great challenges to conventional welding processes, often resulting in defects including incomplete penetration, porosity, and poor joint performance in medium-to-thick plate welding. For 4 mm-thick T2 copper, existing single-laser welding techniques fail to simultaneously achieve both welding efficiency and joint quality, thereby limiting their application in high-demand scenarios. Therefore, it is of great practical necessity to explore more suitable welding methods to achieve high-quality joints in medium-to-thick T2 copper plates while preserving their essential properties.

Taking 4 mm-thick T2 copper plates as the research object, welding experiments were conducted using the infrared-blue hybrid laser welding technology. Firstly, through theoretical analysis, the interaction mechanisms between dual-wavelength lasers and copper materials were clarified, and a series of welding experiments were designed. Specifically, the infrared laser power and blue laser power were selected as variables to optimize the welding process parameters. After welding, the weld morphology of the joint was observed, the microstructure of the weld zone was analyzed, and the mechanical property tests (tensile strength, elongation after fracture, microhardness) and electrical conductivity tests of the joint were carried out.

When the infrared laser power was 5.1 kW, the blue laser power was 1.5 kW, and the welding speed was 20 mm/s, favorable welded joints were obtained. The weld showed an “upper-wide and lower-narrow” shape (Fig.5a), and a dense grain structure was formed in the central area. Tensile tests indicated that the tensile strength of the joint reached 254.42 MPa, the elongation after fracture could reach 14.73%, and the microhardness at the center of the weld peaked at 59.8 HV (Fig.6b). Electrical conductivity tests showed that the electrical conductivity of the weld zone reached 85.23%~90.73% of that of the base material (Table 3).

This study investigates the infrared-blue hybrid laser welding of 4 mm-thick T2 copper plates. With the optimized process parameters (infrared laser power of 5.1 kW, blue laser power of 1.5 kW, and welding speed of 20 mm/s), high-quality welded joints with dense microstructure, excellent mechanical properties, and high electrical conductivity are obtained. The research results provide a basis for high-quality laser welding of copper alloys and have potential application value in the field of medium-to-thick copper plate joining.