EFFECT OF THERMOSOLUTAL CONVECTION ON MORPHOLOGICAL STABILITY OF Al/AlLi EUTECTIC DURING DIRECTIONAL SOLIDIFICATION

The effects of thermosolutal convection on morphological stability were studied during Al/AlLi eutectic growth subjected to vertically upward directional solidification of two hypoeutectic Al-Li alloys.It is shown that thermosolutal convection was weak and was not enough to induce morphological instability of interface at the initial stage.The crystal structure was perfect Al/AlLi eutectic.When thermosolutal convection was strong, the plane interface broke down and grew into single phase cells ahead of the interface.Eutectic phases formed between single phase cells.And,the requirement for stability of eutectic growth in two hypoeutectic Al-Li alloys was also established.