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Continuous Welding of Al-Mg-Si Alloys with Nd: YAG Laser Irradiation: Tensile Properties Optimization of T-joint Seams
E. Cicalã, G. Duffet, H. Andrzejewski and D. Grevey

In the aeronautical industry there is an increasing interest in joining Al alloy sheets using laser welding techniques rather than the riveting ones. The present paper presents experimental results obtained when laser welding Al-Mg-Si sheets in a T-joint configuration (a widely used configuration in aircraft construction) with a Nd:YAG laser. By applying the experimental designs method it is possible to define quantitatively the parameters that produce a T-joint with adequate mechanical properties and prevent hot cracking – a phenomenon that frequently occurs in the laser welding of theses alloys. The experimental approach involved two welding techniques: a sequential one, with a successive movement of the laser beam along each side of the assembly; and a simultaneous welding technique, with two beams moving simultaneously on both sides of the assembly. The two methods gave different results in terms of seam penetration but not in terms of ultimate tensile load. In addition, an empirical model was established for the ultimate tensile load of the seams and a technological window for high tensile properties T-joint was determined: welding speeds between 4 and 5 m/min where fractures were recorded in the base material and a filler wire volume of 0.65 to 0.78 mm3 per mm of weld. The experimental design method allows one to find a more efficient way of determining the optimal domain for complex processes.

Keywords: Nd:YAG laser, laser welding, aluminium alloys, tensile properties, hot cracking

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