Single pass laser-MIG hybrid welding of 8-mm thick pure copper (T2) without preheating: Microstructure and properties

Hybrid laser-MIG welding of 8-mm thick highly reflective pure copper (T2) butt joint with a Y-shape groove was conducted. Welding parameters were optimized based on a five factors and four levels orthogonal experimental design. The surface morphology, microstructure, microhardness, mechanical properties, thermal diffusivity, electrical conductivity, and electrochemical performance of welded joint were studied and analyzed systematically. Fusing zone (FZ) and heat affected zone (HAZ) were made of large-sized columnar grains and grown equiaxed grains, respectively. The tensile strength and elongation of welded joint separately took up 82.1% and 96.8% that of base metal (BM). The decreasing mechanical property of the joints was mainly because FZ and HAZ of the joints presented apparent softening, which made the minimum microhardness of FZ and HAZ account for 69.9% and 59.2% that of BM, respectively. The minimum electrical conductivity and average thermal diffusivity of the joints separately decreased by 62.0% and 34.7% that of BM owing to the large amount of microvoids with a diameter ranging from 1 to 2 µm and impurities including C, Si, Mn and Sn in FZ. The anti-corrosion properties of the joints were lower than that of BM, due to the large-sized grains in FZ and HAZ.