熔体热历史对Al-Cu合金定向凝固界面稳定性的影响

INFLUENCE OF MELT THERMAL HISTORY ON THE UNIDIRECTIONAL SOLIDIFICATION INTERFACE STABILITY OF Al 4.65%Cu ALLOY

在温度梯度、抽拉速率等工艺参数相同的条件下，发现熔体热历史对Ａｌ４．６５％ Ｃｕ 合金定向凝固界面稳定性具有显著影响，它是非平衡溶质分配系数ｋ 增加界面稳定性和结晶过冷度Δｔ－ 降低界面稳定性的综合作用结果． 随着过热处理温度的提高，ｋ 对平衡溶质分配系数ｋ０ 的偏离增大， 导致液固界面稳定性增加；但当过热处理温度进一步提高到使合金熔体结晶的热力学过冷度Δｔ－ 明显增大时， 反而导致液固界面稳定性下降．

Under the same conditions of technological parameters, as thermal gradient, withdrawal velocity, etc, it was found for the first time that the melt thermal history had important influence on the solid/liquid interface stability of Al 4.65%Cu alloy in the unidirectional solidification. With the increasing of the temperature of the melt superheating treatment, the solid/liquid interface stability increased because of the increasing of the deviation of the non equilibrium solute distribution coefficient k to the equilibrium solute distribution coefficient k 0 . On the contrary, the interface stability would decrease when the superheating temperature increased enough to make the melt thermodynamic undercooling Δt - to be increased evidently. Thus, the interface morphological stability depends on the coupling effects of k and Δt - .