Laser Welding Introduced Segregation and its Influence on the Corrosion Behaviour of Al-Cu-Li Alloy

In the present study, the microstructure and corrosion behaviour of laser beam welded 2A97 alloy are investigated. Welding process results in segregation of alloying elements within the fusion zone and, consequently, formation of T1 (Al2CuLi), TB (Al7Cu4Li) and R (Al5CuLi3) phase interdendritic intermetallics. The distribution of the interdendritic intermetallics is non-uniform across the weld. In NaCl solution, corrosion initiates at interdendritic intermetallic with selective dissolution of Al and Li, resulting in a copper-rich remnant, which subsequently acts as effective cathode supporting the dissolution of alloy matrix. The equiaxed dendrite zone at the centre of the weld is most susceptible to corrosion.