枝晶生長過程的相場法模擬
(蘭州理工大學 甘肅省有色金屬新材料省部共建國家重點實驗室，蘭州 730050)
摘 要: 基于Wheeler模型和Eggleston修正強界面能各向異性的方法，建立耦合溶質(zhì)場和溫度場的相場模型，模擬強界面能各向異性下Ni-Cu合金枝晶生長過程。結(jié)果表明：在強界面能各向異性作用下，界面方向枝晶生長不連續(xù)且枝晶出現(xiàn)棱角；由于枝晶尖端溫度梯度和溶質(zhì)梯度較大，枝晶生長迅速。當界面能各向異性強度低于臨界值時，枝晶尖端生長速度隨界面能各向異性強度的增加而增大；當界面能各向異性強度等于臨界值時，枝晶尖端生長速度下降4.34%；當界面能各向異性強度大于臨界值時，枝晶尖端生長速度隨界面能各向異性強度的增加先增大到極大值后逐漸減小。當無量綱熱過冷度較小時，晶體平衡形貌為類矩形；隨著無量綱熱過冷度的增加，晶體平衡形貌向枝晶轉(zhuǎn)變，枝晶尖端生長速度先呈冪指數(shù)增加，然后呈線性增加，枝晶生長由擴散控制轉(zhuǎn)變?yōu)閯恿W控制。
關(guān)鍵字: Ni-Cu合金；界面能；各向異性強度；過冷度；相場法；枝晶生長
binary Ni-Cu alloy with anisotropy of strong interface energy
（State Key Laboratory of Gansu Advanced Nonferrous Metal Materials,
Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:Based on the Wheeler model and the Eggleston regularization technique of the anisotropy of strong interface energy, the phase-field model was built by coupling the solute field with temperature field, and the dendrite growth process of the anisotropy of strong interface energy of Ni-Cu alloy was simulated. The results show that the variation of interface orientation discontinuous and the corners form on the dendrite with the anisotropy of strong interface energy, the dendrites grow fast due to the large temperature gradient and solute gradient. With an increase in anisotropy strength, the growth velocity of dendrite increases when the anisotropy strength is lower than the critical value; when the anisotropy strength equals the critical value, the growth velocity drops down by about 4.34%; with an increase again in anisotropy strength (larger than the critical value), the growth velocity reaches the maximum value and then tends to decrease. The equilibrium morphology of the crystal grows into a square-like one in the situation of low dimensionless supercooling degree; with an increase in dimensionless thermal supercooling degree, the equilibrium morphology of the crystal changes from square-like to dendrite, the growth velocity of dendrite increases exponentially and then increases linearly, and the dendrite growth is under control from diffusion to kinetics.
Key words: Ni-Cu alloy; anisotropy strength; interface energy; supercooling degree; phase-field method; dendrite growth
