Experimental investigation of the hot cracking mechanism in welds on the microscopic scale

The results of the accurate experimental observations on binary Al-Si alloys are presented, which clearly demonstrate that the solidification cracking is a result of the accumulation of macroscopic tensile displacement in a microscopic intergranular liquid film of segregates at the final stage of the weld metal solidification. The reconstructed mechanism of crack initiation provides a clear phenomenological interrelation between the cracking susceptibility, parameters of the welding process and properties of the base and filler material. The correspondent numerical model takes into account the effects of displacement accumulation as well as the influence of thermodynamical and thermo-mechanical properties of the welded material. It is successfully applied for development of technological means for elimination of the solidification cracking during welding of aluminium alloys AA6056, such as a multi-beam welding.