Al-Cu 合金高梯度定向凝固过程中的形态转变

本文利用 ZMLMC 定向凝固装置,研究了 Al-Cu 合金系在不同温度梯度下定向凝固时凝固界面和组织形态的变化。发现存在着两种树枝状生长和胞状生长之间的转变,即在低速范围内胞状向树枝状转变,在高速范围内树枝状向胞状转变;当温度梯度足够高时,可以在整个生长速率范围内不出现树枝状生长,获得高度细化的胞状组织;合金的结晶温度间隔越宽,完全消除树枝状生长所需的温度梯度越高。

MORPHOLOGICAL TRANSITIONS DURING DIRECTIONAL SOLIDIFICATION UNDER HIGH THERMAL GRADIENT

Changes of interface morphologies and microstructures of Al-Cu alloysduring directional solidification under different thermal gradients were investigated by us-ing a ZMLMC directional solidification apparatus.It was found that there exist two kindsof morphological transitions between cellular and dendritic growth.One of them iscell-to-dendrite transition at low growth rates and another is dendrite-to-cell at highgrowth rates.With enougth high thermal gradient dendritic growth can be erased withinthe whole growth rate range and highly refined microstructures can be obtained.The widerthe temperature interval of crystallization of an alloy,the higher the thermal gradient need-ed to erase the dendritic growth.