张红伟，NAKAJIMA Keiji，王恩刚，赫冀成

(1. 东北大学 材料电磁过程研究教育部重点实验室，沈阳 110004；2. Division of Applied Process Metallurgy, Department of Materials Science and Engineering,Royal Institute of Technology (KTH), Stockholm SE-10044, Sweden)

Al-Si合金宏观偏析、凝固组织演变的元胞自动机-控制容积法耦合模拟

张红伟1，NAKAJIMA Keiji2，王恩刚1，赫冀成1

(1. 东北大学 材料电磁过程研究教育部重点实验室，沈阳 110004；2. Division of Applied Process Metallurgy, Department of Materials Science and Engineering,Royal Institute of Technology (KTH), Stockholm SE-10044, Sweden)

建立凝固过程中宏观流动、传热、溶质传输与微观形核、生长过程双向耦合数学模型，并针对Al-Si二元合金凝固过程进行二维元胞自动机−控制容积积分法(CA−FV)耦合模拟。模型反映了流场下晶体逆流生长特性，考虑了温降导致的形核和生长以及形核和生长引起的固相分率变化对宏观场的影响，能预测凝固过程中再辉和晶间偏析等现象，反映合金液流动对合金的溶质分布以及凝固组织形貌的作用规律。与仅宏观传输模拟结果和无流动影响的模拟结果进行了对比，验证了耦合模型的优越性。同时考察了铸型尺寸对凝固组织形貌的影响。

Al-Si合金；凝固；晶体生长；宏观偏析；元胞自动机−控制容积积分法

Abstract:A coupled cellular automaton−finite volume (CA−FV) model for macroscopic fluid flow, heat transfer, solute transport and microscopic nucleation and grain growth procedure was developed and applied in an Al-Si binary alloy solidification process. The model reflects the dendrite growth kinetics in the presence of fluid flow, the nucleation and growth in CA scale due to the increase of undercooling, and the feedback of solid fraction and temperature to FV nodes due to the nucleation and growth. The coupled CA−FV model can predict the recalescence and the intergranular segregation during alloy solidification process, which shows great advantages compared with the results by FV model and CA−FV model without fluid flow. The effects of fluid flow on the solute distribution and the solidification morphologies,as well as the influence of ingot size on the solidification structures, were discussed with the CA−FV model.

Key words:Al-Si alloy; solidification; grain growth; macrosegregation; cellular automaton−finite volume method

合金的凝固过程涉及宏观传输(传热、传质、流动)、相变热力学(相平衡、相界面、化学衡)与凝固动力学(溶质再分配、形核、生长)等多种复杂现象。鉴于宏观传热、传质和流动影响微观形核和生长的温度和浓度条件，而微观形核和生长释放的潜热又反过来影响温度和溶质等宏观场的分布，因此，有必要将宏观传输过程与微观形核生长过程相结合，通过建立合理的数学模型，获得更符合实际凝固过程的模拟结果，实现对凝固组织的预测和控制，从而获得需要的合金制品的质量及性能。……