A New Three-dimensional Multi-scale Model to Predict Hot Cracking within a Weld Pool of Aluminum Alloys

A new multiscale solidification-thermomechanical model is developed to simulate the transient force field deforming fusion semisolid welds as a function of welding parameters. The model consists of two major modules: 1) By means of the granular modelling of solidification, the microstructure of the semisolid area within the weld is reconstructed in three dimensions. The semisolid structure is composed of solidifying grains and a network of micro liquid channels lying along the grain boundaries. The developed microstructure also varies by welding parameters. 2) Through the finite element method, the mechanical interaction between the semisolid weld and its base metal is studied to capture the transient force field deforming the semisolid weld. Thermomechanical stresses and shrinkage stresses are both considered. The shrinkage displacements acting as the Dirichlet boundary condition on the base metal are extracted from the previous stage where the solid fraction can be extracted as a function of time and position. The model is then used to study the effect of welding parameters including welding current, welding velocity and also welding constraint on the transient deformation of the semisolid weld.