本文选择了水平方向、由下向上及由上向下三种定向凝固工艺,对Al-4.5%Cu及Al-4.5%Cu-0.5%Mn合金的反偏析规律进行了研究。结果表明,枝晶组织对反偏析有极大影响,对于细小的等轴晶组织几乎不存在反偏析。Kirkaldy和Youdelis的反偏析理论只适用于柱状晶组织,对于等轴晶及等轴晶-柱状晶混合组织,作者对此理论进行了修正。溶质引起的流动对反偏析也有着重要影响,这种影响可归结为对一次晶固相浓度及固—液共存区的液相浓度的改变。 In this paper, the horizontal segregation of Al-4.5% Cu and Al-4.5% Cu-0.5% Mn alloy was studied by three directional solidification processes: horizontal direction, downward direction and upward direction. The results show that the dendritic microstructure has a great influence on the de-segregation, and there is almost no de-segregation for the fine equiaxed grains. The theory of the anti-segregation of Kirkaldy and Youdelis is only applicable to the columnar crystal structure, and the author has revised this theory for the equiaxed and equiaxed crystal-columnar mixed structure. Solute-induced flow also has an important effect on de-segregation, a factor that can be attributed to changes in the liquid-phase concentration of the primary crystalline solid phase and the solid-liquid coexisting zone.