(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等提出的純擴散相場模型，建立耦合溶質(zhì)場、溫度場和流場的相場模型，采用有限差分法對控制方程進行數(shù)值求解，研究Ni-Cu合金凝固過程中單晶粒枝晶和多晶粒枝晶在強制對流作用下的生長行為。結(jié)果表明：熔體的流動顯著改變凝固前沿的傳熱和傳質(zhì)，從而改變枝晶的生長行為。在流速為6.43 m/s的垂直強制對流作用下，上游枝晶受過冷熔體沖刷，枝晶尖端溶質(zhì)濃度和溫度低，實際過冷度大，枝晶生長迅速，穩(wěn)態(tài)生長速度比純擴散時增加28%；熱量和溶質(zhì)在下游富集，下游枝晶尖端溶質(zhì)濃度和溫度高，實際過冷度小，枝晶生長緩慢，穩(wěn)態(tài)生長速度比純擴散時減小26%。
關(guān)鍵字: Ni-Cu合金；相場法；強制對流；枝晶生長；凝固；溶質(zhì)場；溫度場；流場
（State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials,
Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:Based on the Wheeler model, the phase-field model was built by coupling with the concentration field, temperature field and flow field. An explicit finite difference numerical method was used to solve the phase-field model equations and simulate both of the single and multi-grain dendritic growth of Ni-Cu alloys in a forced flow. The results show that the fluid flow alters the local heat and solute transfer at the solidification front, thus the dendritic growth behavior is significantly influenced. Under forced flow with a flow velocity of 6.43 m/s, the temperature and the concentration of the upstream dendritic crystal are low because of the undercooled melt flushing, the greater actual supercooling of the upstream dendritic crystal makes the dendritic crystal become fast, the tip velocity at steady state increases by about 28% compared with the case without flow. The heat and solute are enriched in the downstream, the temperature and the concentration of the downstream dendritic crystal are high, the less actual supercooling of downstream dendritic crystal makes the dendritic crystal growth become slow, the tip velocity at steady state decreases by about 26% compared with the case without flow.
Key words: Ni-Cu alloy; phase-field; forced flow; dendritic growth; solidification; concentration field; temperature field; flow field
