INFLUENCE OF CRYSTALLOGRAPHIC AND HEAT-FLOW ORIENTATIONS ON GROWTH OFCELLULAR DENDRITES

A numerical program has been developed in order to calculate the time- dependent thermal gradient and isotherm velocity within a solidifying pool obtained by stationary laser treatment. The heat diffusion equati on is solved for an axisymmetric geometry with an enthalpy formulation using a standard FDM implicit scheme. The program has been used to in vestigate to which extent the cellular dendritic growth orientation is affected by the direction and amplitude of the thermal gradient. Expe riments were carried out on Al-1 mass%Si dendritic single crystals ori ented by Laue back reflection technique and cut along precise crystall ographic orientations prior to laser irradiation and on Al-33mass%Cu e utectic polycrystalline alloys. Deviation of cellular dendritic growth direction from crystallographic and heat flux directions are reported . In addition, the comparison of the microstructural spacings with the oretical predictions outlines the influence of crystallography on the microstructural development during stationary laser treatment.