Laserstrahlschweißen von hochfesten Aluminiumlegierungen

Aerospace industry requires materials with high specific strength and good corrosion resistance. Aluminium alloys accomplish these tasks, but are difficult to weld, because of their good thermal conductivity and high reactivity with atmospheric gases. Hence, solved gases lead to porosity in the weld seam. For aerospace applications these alloys are usually riveted or glued. Electron beam welding is difficult to apply, because of the required vacuum. Using high power CO2-Lasers for welding, a heat source with a high intensity is available, too, but there is the disadvantage of good reflectivity. The following paper will show CO2-Laser welding of conventional and aerospace Al-Alloys. First typical welding defects like pores and cracks and their reasons are discussed. Than the paper will outline, how to improve laser weldability of Al-Alloys. The welds are characterized by X-ray and metallographical investigations, hardness measurements and mechanical tests. It will be shown that it is possible to weld Al-Alloys within a range of power flux density 1,5 — 2,5 × 106 W/cm2 with a proper strength and elongation. A chemical-mechanical surface treatment is necessary before welding and a protection with inert gases during the process.