定向凝固生长速率对Al-15Cu合金组织演化的影响

Effects of Directional Solidification Growth Rate on Microstructure Evolution of Al-15Cu Alloy

通过定向凝固装置在10、20、50μm/s凝固速率下制备了Al-15Cu合金试样。在不同凝固速率下,溶质元素Cu在试样中的分布均符合Scheil方程。由于Cu密度较大,产生密度偏析,使得有效分配系数kE增大,且凝固速率越小,密度偏析越严重。凝固速率的增加或液相中溶质浓度的升高,一方面使得溶质元素Cu在固液界面处的富集程度升高,抑制了枝晶宽度的增加,细化了组织;另一方面促进了成分过冷,树枝晶特征更加显著。

Al-15Cu alloy samples were prepared by directional solidification device with solidification rates of 10,20 and 50μm/s.The distribution of solute element Cu conforms to Scheil equation under different solidification rates.Due to the high density of Cu,gravity segregation occurs,which makes the effective distribution coefficient kEincrease.With decreasing in the solidification rate,the gravity segregation becomes more serious.With the increase of the solidification rate or solute concentration in the liquid phase,the concentration of solute element Cu at the solid-liquid interface is increased,inhibiting the broadening of dendrite and refining the structure.Meanwhile,the component supercooling is promoted with the dendrite characteristics more obvious.