CO2 laser welding of the aluminium aerospace alloy AA2024

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CO2 laser welding of the aluminium aerospace alloy AA2024

Kokkonen, J. / Ion, J.C.

Aluminium alloys are used in a wide range of industrial sectors because of their low density, good structural properties and resistance to corrosion. However, they are difficult to join using fusion welding techniques. Mechanical fastening methods therefore currently dominate in critical applications, notably in the aerospace industry. Laser welding provides many advantages compared with mechanical fastening, but little information is available concerning welding procedures and weld properties for commercial aluminium alloys. The main objective of this study was therefore to develop a reproducible CO2 laser welding procedure for the aluminium aerospace alloy AA2024, which achieves both the most stringent (class B) workmanship standards of current European guidelines, and industrial mechanical property requirements. Butt welds were made in sheets of thickness 1.6 mm, using a range of laser beam parameters, various process gases and two different filler wires. With respect to the appearance of the weld, quality class B was achieved using the following principal parameters: 3.5 kW worpiece beam power, 4 m/min welding speed, AA2319 filler wire, argon shielding gas, and argon-50 % helium plasma control gas. Porosity in the weld bead also met class B quality requirements. Hardness values were close to industrial recommendations. The average ultimate tensile stress was about 75 % of that of the base material. The fatigue properties exceeded the requirements specified by the International Institute of Welding for single-sided welds, and almost met those pertaining to welds made from both sides. The quality of the weld toe was found to have the largest effect on mechanical properties. Improved mechanical performance can be expected if the weld bead is machined flush prior to testing, or if a smoother transition from the weld bead to the base material can be achieved. CO2 laser welding appears to offer a promising alternative to both TIG welding and mechanical joining, particularly in applications where high productivity is a requirement.