Al-Li合金定向凝固的热溶质对流

THERMOSOLUTAL CONVECTION DURING DIRECTIONAL SOLIDIFICATION OF Al-Li ALLOYS

研究了亚共晶二元 Ａｌ－Ｌｉ合金垂直向上定向凝固期间热溶质对流对共晶生长的影响．结果表明，晶体生长初期，对流对共晶生长影响较小，能够获得规则的共晶组织．当存在非稳定性对流时，在生长方向上，β相（ＡｌＬｉ）呈非连续的短棒结构；在水平方向上，β相里波形排列．并且还发现，非稳定性对流中存在着最不稳定波，且这种波对共晶生长的影响最强烈，它使共晶组织粗大．并且迎着流体流动方向生长。

The effect of thermosolutal convection on eutectic growth was studied during vertically upward directional solidification of binary hypoeuectic Al-Li alloys. It is shown that the effect of convection on eutectic growth is little at the initial stage, and the regular eutectic structure can be obtained. Unstable convection may have a strong influence on eutectic growth, and P phase showed ' noncootinuous short rodlike structure in the vertical direction. A wave-like arrangement of g phase exists in the horizontal direction. Moreover, there is most unstable wave in the unstable convection during crystal growth. The effect of the most unstable wave on eutectic growth is strongest, which make the eutectic structure coarse and crystal grow against the direction of fluid flow.