Study on the microstructure of Al-Mg-Si-Cu alloy semi-continuously cast near liquidus

The semi-continuously cast near liquidus process is used in casting Al-1.2Mg-0.8Si-0.4Cu alloy.The influence of different casting temperatures and velocities on the microstructure of semisolid slurry is studied.The microstructure is very nonuniform when the billet is cast at 750 ℃,the edge microstructure consisting of small grains,but coarse dendrites appear in the 1/2R and the center part.The diameter of the smallest grain is 25 μm and that of the largest one is 220 μm When the billet is cast after being held for a few minutes at 660 ℃ the microstructure with uniform,small and globular grains can be attained.The average grain size is 36.5 μm.It is beneficial for fine,uniform and near globular microstructure to form when the casting velocity is 150 mm/min.The results indicate that the ideal semi-solid slurry can be obtained by the semi-continuously casting near liquidus.