Al-Mg-Si-Cu合金近液相线半连续铸造组织研究

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

采用近液相线半连续铸造方法制备了Al-1.2Mg-0.8Si-0.4Cu合金半固态锭坯,研究了浇注温度和铸造速度对锭坯微观组织的影响.合金熔体在750℃下浇注,组织不均匀,边部是细小的晶粒,1/2半径和中心部位是粗大的枝晶,最小晶粒直径25μm,最大晶粒直径达220μm;660℃保温后浇注,可以获得适合半固态加工的均匀、细小的近球形组织,锭坯中心和边部组织差异小,平均晶粒尺寸为36.5μm;铸造速度达150 mm/min时有利于均匀、细小的近球形组织形成.结果表明,对于Al-1.2Mg-0.8Si-0.4Cu铝合金采用近液相线半连续铸造可以获得理想的半固态浆料.

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. 5μm. 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.