Analytical Description of the Influence of the Welding Parameters on the Hot Cracking Susceptibility of Laser Beam Welds in Aluminum Alloys

The grain structure of a weld seam influences its susceptibility to hot cracking during the welding process. The previously derived explicit analytical expressions allow for the accurate prediction of both the morphology of the grain structure and the grain size in a wide range of processing parameters. This model is now combined with the pressure balance model of Rappaz, which describes the formation of hot cracks by the balance between solidification shrinkage and thermomechanical deformation. The combination of the two models allows for the description of the impact of the welding parameters on the strain rate limit that a laser welded seam can withstand without the formation of hot cracks. It reveals that the absorbed line energy per depth is the key parameter to influence the value of this limit. The model was validated for the case of laser beam welding of the technical aluminum alloy AA6016. The calculated critical strain rates agree well with the experimentally determined critical strain rates measured by means of digital image correlation.