Influence of the solidification path of AlMgSi aluminium alloys on the critical strain rate during remote laser beam welding

The solidification paths of aluminium alloys have a major influence on the susceptibility to hot cracking during laser beam welding. The model of Rappaz, Drezet and Gremaud allows to predict the susceptibility to hot cracking of an alloy as a function of its solidification path by means of a critical strain rate. The direct relation between the solidification path and the critical strain rate as stated by the model was confirmed experimentally. For this purpose, AlMgSi alloys with different silicon contents were used to obtain laser beam welds, which solidify along different solidification paths. The corresponding critical strain rates were experimentally determined by means of digital image correlation. The low susceptibility to hot cracking of the investigated aluminium alloys, especially designed for remote laser beam welding, could be attributed to the positive influence of their high amount of silicon on the solidification path.