MORPHOLOGICAL TRANSITIONS DURING DIRECTIONAL SOLIDIFICATION UNDER HIGH THERMAL GRADIENT
Al-Cu 合金高梯度定向凝固过程中的形态转变

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.