Strength improving mechanism of laser arc hybrid welding of wrought AA 2219 aluminium alloy using AlMg 5 wire

Abstract

Laser arc hybrid welding of wrought AA 2219 aluminium alloy was studied. The cross-weld tensile strength of the joint using AlMg₅ wire was 20% higher than that using AlCu₇ wire. The reasons for strength improvement were analysed by microstructure observations via scanning electron microscopy, transmission electron microscopy and electron backscattering patterns. The results showed the strength improvement of the joint using AlMg₅ wire depended on two reasons. One is the formation of large amount of fine S–Al₂CuMg precipitates. The other is the preformed pinning effect of the precipitates on the dislocations. Finally, the formation of the fine S–Al₂CuMg precipitates of the joint using AlMg₅ wire was discussed by thermodynamic calculation, and the formation of the preformed dislocation pining effect was discussed by the collision theory of adjacent dendrites during solidification.