Al-Cu-Zn合金单相凝固过程中的溶质截留

SOLUTE TRAPPING DURING THE PRIMARY SOLIDIFICATION OF Al-Cu-Zn ALLOY

在连续生长模型(CGM)基础上,提出了三元合金溶质截留过程中的驱动自由能和界面温度的计算公式,模拟了Al-Cu-Zn合金单相凝固过程中的溶质截留和界面温度行为.在合金两个不同等深面上,界面移动速度增加时,固相线和液相线向同素异型相界T0曲线靠近;随生长速度的增大,分凝系数急剧增加,在界面速度接近溶质扩散速度时,发生完全溶质截留现象,在速度比较低时的计算表明,合金的平衡分凝系数可在冷却速度小于7.1 K/s的凝固过程使用;固相成分一定时,界面温度随生长速度增加而上升,在溶质扩散速度vD处达到极值后界面温度下降;但液相成分一定时,界面温度随生长速度增加而下降.

The formula to calculate the driving Gibbs energy and interface temperature during solute trapping in the ternary alloy is present on base of the continuous growth solute trapping model of Aziz and Kaplan, and used to model the solute trapping behavior during the primary solidification of Al-Cu-Zn alloys. The kinetic solidus and liquidus approach to T-0 curve with increasing growth velocity on two different isopleths of the alloys. The solute trapping coefficient increases sharply with increasing speed, and the equilibrium partitioning coefficient can be used reasonably for the solidification with cooling rate below 7.1 K/s. In condition of fixed solid composition, the interface temperature rises with increasing velocity and reaches its peak near the solute diffusive speed nu(D), however, for fixed liquid concentration, the interface temperature decreases for increasing growth speed.