二元合金非等温凝固枝晶生长的数值模拟

采用相场方法对二元合金的非等温凝固进行二维数值模拟.以Ni-Cu合金为例,研究了在不同热扩散系数和不同溶质梯度系数下枝晶的生长以及二元合金的溶质分布.研究结果表明,随着热扩散率的增大,包围等轴晶的热扩散层增厚,抑制了侧向分支的生长,从而使侧向分支生长不发达;其次,热扩散率的增大,使得溶质场扩散层也明显增厚,溶质截留现象不明显,但在溶质场界面前沿产生明显溶质偏析;当溶质梯度系数增大时,相场形貌厚度并不产生影响,但溶质场扩散厚度却显著增加,而溶质偏析程度得以降低.

Numerical simulation of dendrite growth for binary alloy during non-isothermal solidification

A phase-field method for two-dimensional numerical simulation of non-isothermal binary alloy solidification was studied.The dendrite growth and the solute distribution were formulated with various thermal diffusion coefficients and solute gradient coefficients for Ni-Cu binary alloy.The result of the calculation indicates that the thermal diffusion layer collected around the equiaxed dendrite tends to become thicker with the increment of diffusivity and the growth of side-branches are restrained,so that the second dendrite arms are undeveloped.At the same time,the diffusion of the solute field becomes thicker too,the phenomenon of the solute trap becomes inconspicuous,but the solute segregation comes remarkably into being at the verge of the solute field.With the increment of the solute gradient coefficient,there is no influence on the morphology of the dendrite with,but the solute diffusion layer collected around the equiaxed dendrite becomes thicker notably,and the degree of the segregation is reduced.