Continuous welding of Cu–Ni dissimilar couple using CO₂ laser

The evolution of microstructure during continuous laser welding of dissimilar metals has been studied for a binary Cu–Ni couple. The effects of laser beam scan speed and laser power on the shape and size of the melt pool, the weldment–substrate interface, the composition profiles, and microstructures of the weldments have been investigated. It is shown that the melt pools exhibit a characteristic asymmetry in shape. The observed microstructure is characterised by the existence of compositional and microstructural variations leading to a banded appearance suggesting localised mixing. Distinct differences exist in the evolution of the microstructure in the copper and nickel sides of the weld pool. An attempt is made to explain some of the experimental observations using thermodynamic and thermal transport arguments.