过冷度对Ni-Cu合金枝晶偏析影响的相场法模拟

Numerical simulation for influence of super-cooling degree by phase-field method on microsegregation of nickel-copper alloy

采用耦合热扰动的相场模型,对Ni-Cu合金枝晶生长中的枝晶形貌和微观偏析进行计算和分析,并研究过冷度对其凝固过程中溶质分布的影响。结果表明:随着过冷度的增加,二次枝晶变的更发达,枝晶主干变细,一次枝晶干轴对称中心处的溶质浓度升高,一次枝晶干和二次枝晶臂间富集的溶质更多。过冷度越大,固液界面前沿溶质扩散层越薄,枝晶的微观偏析越严重,即溶质微观偏析程度随过冷度的增大而增大。

Based on KKS model coupling the phase field and concentration field,the dendritic growth process model for Ni-Cu alloy during isothermal solidifications was developed.The solute distribution of nickel-copper alloy during the metal solidification was simulated,the effects of supercooling(ΔT) on the highest solute concentration in front of the dendrite tip and solute segregation ratio were studied emphatically.The results indicate that,the larger the supercooling ΔT is,the higher the concentration maximum value in front of the dendrite tip is,the severer the microsegregation is.The supercooling can trigger the growth of the secondary arms and increase the growth rate of the primary dendrite.As the supercooling increases,the microsegregation increases.