3-D multi-scale modeling of deformation within the weld mushy zone

The deformation of the fusion weld mushy zone, as a critical factor in solidification cracking, has been simulated by combining a 3D multi-scale model of solidification and microstructure with a deformation model that includes the effects of solidification shrinkage, thermo-mechanical forces and restraining forces. This new model is then used to investigate the role of welding parameters on the deformation rate of micro liquid channels during Gas Tungsten Arc welding of AA6061. It is shown that the internal normal deformation rate due to solidification shrinkage and also the external normal deformation rate caused by external forces are both highest for the micro liquid channels at the center of the mushy zone where solidification cracks usually occur. Furthermore, the model shows that welding travel speed and welding current strongly influence the deformation rate of the weld mushy zone and consequently the solidification cracking susceptibility of the weld. The model can be also used to link micro-scale phenomena with the macro-scale characteristics of solidification cracking during welding.