Non-steady 3D dendrite tip growth under diffusive and weakly convective conditions

Three dimensional α-Al dendrite tip growth under varying solute gradients in an Al-Cu-Si alloy melt has been studied using real time synchrotron X-ray imaging and mathematical modelling. X-radiographic image sequences with high temporal and spatial resolution were processed and analysed to retrieve three-dimensional spatial details of the evolving dendrite and the solute concentration field, providing vastly improved estimates for the latter, in particular for the melt regions adjacent to the dendrite tips. Computational results obtained from an extended Horvay-Cahn dendrite tip model, capable of taking into account the effects of sample confinement, showed good agreement with the experimental data, and can be taken to verify the robustness of the 3D data extraction protocol.