Abstract: The effects of Ce on the planar, cellular and dendritic interface stability, and the primary and secondary arm spacing have been investigated under directional solidification conditions in this paper. With the help of the investigation, the role of common elements in the solidification process is analysed and discussed. The results show that Ce decreases the stability of the interface; for planar growth, least squares linear regression analyses give the relationship between the critical value of G/V and Ce content as follows: G/V = 0.38[4.5+ (2~3) Cce] (A1-4.5%Cu). Ce decreases the primary arm spacing for the low Ce content regime but increases the primary spacing for the high Ce content regime. The secondary arm spacing decreases with the increase in Ce content. The analyses show that the microelements have apparent effects on the solidification process of alloys only for them to have very small equilibrium distribution coefficients k and large Co/k.

Key words: 定向凝固, 界面稳定性, 铝铜合金, 稀土元素, 枝晶间距