Characterization of microstructures and growth orientation deviating of Al₂Cu phase dendrite at different directional solidification rates

At different directional solidification rates (10, 20 and 100 μm/s), microstructures and growth orientation variations of Al₂Cu dendrite in Al-40%Cu alloy were characterized. When solidification rates were ranged from 10 to 100 μm/s, three-dimensional microstructure of Al₂Cu dendrite changed from faceted L-shaped patterns to non-faceted complex dendrite morphology in transverse section. By the macro and micro orientation analysis characterize methods, [001] growth direction of Al₂Cu dendrites with different morphologies was determined. The deviation angle between [001] direction and the heat flow direction was increased with solidified rate increasing. The experimental results showed that the regular solidified microstructure and growth orientation along the heat flow direction could be well controlled under lower directional solidification rate.