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Abstract

Solidification under terrestrial conditions is inevitably subject to melt flow, driven by solutal and thermal buoyancy or by forced convection during filling. In this work we present a phase-field study of the transport of the melt and equiaxed dendrites of a Mg-Al alloy in a driven sheer flow. In a first step, columnar dendritic microstructures are calculated under pure diffusive conditions for varying cooling conditions. For these microstructures the permeability perpendicular to the temperature gradient is calculated from the pressure drop during forced melt flow. The permeability will be related to the characteristics of the dendritic structure like primary and secondary arm spacing. In a second step, for selected growth conditions, growth dendritic solidification is simulated in the presence of driven melt convection and compared to the purely diffusive case. In a last step the coagulation of equiaxed structures is investigated for sedimenting dendrites in the absence of externally driven melt flow. Consequences for realistic process simulation in a multi-scale setting are discussed.