Modelling and direct numerical simulation of dendritic structures under solidification conditions during fusion welding

This work is devoted to the numerical modelling and simulation of weld pool fluid flow, temperature field and solidification structures during fusion welding. Thus, two topics out of the global simulation chain outlined above, the macro-modelling and the micro-modelling with a link from the first one to the second will be considered. The macro-modelling of the temperature field and the weld pool geometry were realised usinf a commercial CFD-FEM code. The information obtained from the macro-modelling in form of solidification conditions serves as input data for the subsequent micro-modelling. For the micro-modelling of the solidification structures, a novel model, which is based on a computer code within the framework of this work. The model enables to perform space-resolved simulations of the time evolution of solidification morphologies under constrained solidification conditions in binary alloys. The macro- and micro-models were used to simulate the temperature field, the weld pool geometry and the solidification structures during GTA welding of a low alloyed steel and during electron beam surface remelting of an AlSi alloy. The modelling results were compared with the experimental findings.