Time-dependent directional solidification of binary Al-Cu alloys in the initial transient

At the start of directional solidification a complex interaction between the movement of the solidification front, the concentration pile-up ahead of the front and the temperature gradient at the solid - liquid interface takes place. Experiments with binary Al-Cu1.3 wt.% were performed in this regime in a Bridgman - Stockbarger type gradient furnace allowing solidification with a planar solid- liquid interface. The time-dependent velocity and temperature profiles were measured during the experiments, whereas the concentration profiles were analysed from the processed samples. The experimental results were compared to predictions from numerical simulations based on the model of Coriell et al. Good agreement is obtained in the description of time-dependent diffusive, planar growth in the initial transient.