Pb-Sn合金凝固通道偏析的实验与数值模拟研究

通过实验和数值模拟研究了Pb-19%Sn合金侧向凝固过程中的通道偏析.结果表明:铸锭侧向冷却时,糊状区中的富集溶质(Sn)由于密度小而向上运动.固相分数愈大,枝晶间流动强度愈小.偏析通道中的富集溶质相对于周围凝固时间长;通道由糊状区向最后凝固区域生长.侧向凝固的铸锭在顶部形成正偏析,在底部形成负偏析,在表面形成"沟槽"偏析,在铸锭内部形成A形偏析.基于本文数学模型的数值模拟结果与实验模拟结果一致,可反映侧向凝固与通道偏析的形成规律.

Experimental and Numerical Study on the Formation of Channel Segregation in Pb-Sn Alloy Ingot

The formation of channel segregation during unidirectional solidification from the side of a Pb-19%Sn alloy ingot has been studied by experimental and numerical methods. The obtained results show that the solute-rich liquid in the mushy zone flows upwards because of its lower density. The interdendriteic fluid flow becomes strong when the solid fraction is low. Segregated channels grow from mush towards the last solidification region and the enriched solute in channel solidifies finally. When the ingot is cooled from the mold side, A-type segregates may form in the casting and segregated channels form on the surface, while the positive and negative segregation form in the top and the bottom of the ingot, respectively. The numerical results in this article are consistent with experiments and they indicate the characteristics of the channel segregation formation during the unidirectional solidification from the side of ingot.