Morphology of Interface near Absolute Stable Growth Rate and Crystalline Anisotropy

为了研究Al-Cu合金凝固过程中的微观组织，采用YAG激光对其进行重熔并快速凝固。试样是从单晶中切割出来的，因为初始的微观结构会影响激光处理后的微观结构。以接近绝对稳定的生长速率实现凝固。用扫描显微镜观察了试样的显微组织，用生长速率测量了试样的主臂间距。采用热传导有限元法对枝晶生长速率和界面温度梯度进行了数值计算。观察到的形态为细胞-枝状，臂很短。枝晶初生间距随生长速率的增加而减小，但随着生长速率的增加，减小的幅度越来越小，直至达到绝对稳定。实验结果与理论结果进行了比较。对排列的细胞-树突进行了理论推导，实验结果与预测结果吻合较好。

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.