Autogenous laser welding of AA 2024 aluminium alloy: process issues and bead features

摘要

Laser welding has been proven to be promising for aerospace. Welds with high aspect ratio are produced with lower heat input compared with conventional arc-welding processes; furthermore, higher productivity and lower distortion are benefited. Nevertheless, specific issues must be addressed depending on the material to be welded. In this frame, laser welding of AA 2024 in T3 heat treatment condition, which is among the most common light metal alloys in aerospace, is discussed. A comprehensive review of issues influencing weldability is given, combining ad-hoc trials with Yb:YAG disk-laser source and existing knowledge in the referred literature. Therefore, a number of subjects are investigated: the need for proper gas assistance, the threshold value of irradiance to be overcome for key-holing as a consequence of low absorptance and high conductivity, magnesium vaporization leading to instability and macro-pore formation, softening in the fused zone resulting in lower strength due to dissolution of precipitates and loss of the strengthening phase. EDS inspections, Vickers micro-hardness tests and tensile tests have been conducted to discuss the response. Convincing results have been achieved both in terms of reduction of the heat affected zone and ultimate tensile strength, in comparison with other findings in the literature.