Morphology of Interface near Absolute Stable Growth Rate and Crystalline Anisotropy

为了研究Al-Cu合金在快速凝固过程中的微观组织，采用激光重熔快速凝固的方法对Al-Cu合金进行了研究。样品是从单晶中切割出来的，因为激光处理后的初始微结构会影响最终的微结构。实现了凝固，生长速率接近绝对稳定。用扫描显微镜观察了薄膜的微观结构，并用生长速率测量了一次臂间距。用热传导有限元方法MARC对枝晶生长速率和界面温度梯度进行了数值计算，观察到枝晶的形态为极短臂的胞状枝晶。一次枝晶间距随着生长速度的增加而减小，但随着生长速度的增加，减小的幅度越来越小，直至达到绝对稳定。并将实验测得的初级间距与现有的理论间距进行了比较。建立了排列胞状枝晶的理论，并与实验结果进行了比较，两者吻合较好。

Al-Cu alloy is remelted by YAG laser and solidified rapidly in order to study the micro-tructure in the solidification. Specimen is cut out from the single crystal, because the initial micro-structure will affect the resultant micro-structure after laser treatment. The solidification is realized with growth rate near the absolute stability. The micro-structure is observed by the scanning microscope and the primary arm spacing is measured with the growth rate. The growth rate of dendrite and the temperature gradient at the interface are numerically estimated by the finite element method for heat conduction, MARC.The observed morphology is cellular -dendrite with very short arms. The primary spacing of dendrite decreased with growth rate, but the rate of decrease becomes smaller and smaller with increasing growth rate up to the absolute stability. The experimental primary spacing is compared with the available theoretical one. The theory is constructed for arrayed cellular-dendrite and the agreement between experiment and prediction is shown very well.