相场法模拟中影响侧向分支的相场参数

EFFECTS OF PHASE-FIELD PARAMETERS ON SIDEBRANCHING USING PHASE FIELD SIMULATION

使用耦合热扰动的相场模型,研究相场参数对枝晶侧向分支的影响。结果表明,随着过冷度的增大,包围等轴晶的热扩散层越薄,这越有利于侧向分支的生长,使枝晶侧向分支越发达。各向异性系数ε影响枝晶尖端稳态行为,ε越大,枝晶生长速度越大,侧向分支越发达,二次枝晶间距越小:耦合系数λ越小,尖端生长速度较快收敛于格林函数计算值,侧向分支越发达;热扰动幅值Fu对温度场的影响明显,当Fu取值适当时,热噪声可以引发侧向分支,但是不影响尖端的稳态行为。

The dependence dendritic sidebranching on phase-field parameters is studied by using a phase-field model which incorporates thermal noise quantitatively. The calculated results indicate that, with the increment of undercooling, the thermal diffusion layer collected around the equiaxed dendritic is more thin, which is advantageous to the growth of the sidebranching and the equiaxed dendritic presents the morphology of developed side-branching; The anisotropy parameter ε influence the steady state of the dendrite tip, the larger ε, the quicker the dendrite tip velocity is, the more developed the side-branches are and the smaller the DAS are; The smaller coupling coefficient λ, the quicker the dendrite tip velocity converges on the Green function calculation, the more developed the side-branches are; The magnitude of thermal noise influence temperature field obviously, when appropriate value is assigned to Fu, noise can enhance the emergence of side-branching but does not influence the tip operating state.