數(shù)值模擬
( 1. 南京理工大學(xué) 金屬納米材料與技術(shù)聯(lián)合實驗室，
南京 210094；
2. 東南大學(xué) 材料科學(xué)與工程系，南京 210096)
摘 要: 通過對Al-4.5%Cu合金鑄錠顯微偏析形成的數(shù)值模擬， 研究了凝固路徑對凝固后鑄錠不同位置處顯微偏析參數(shù)的影響。在顯微偏析模型中考慮了樹枝晶粗化、 固相溶質(zhì)逆擴散、 枝晶尖端過冷、 隨溫度變化的溶質(zhì)擴散系數(shù)等影響顯微偏析形成的動力學(xué)因素。 數(shù)值方法中采用變網(wǎng)格技術(shù)跟蹤移動界面，通過迭代求解溶質(zhì)擴散方程和溶質(zhì)守恒方程計算顯微偏析參數(shù)。 結(jié)果表明， 對于Al-Cu合金， 固相擴散主要由溶質(zhì)擴散速率控制，而非局部凝固時間。 顯微偏析參數(shù)不僅取決于局部凝固時間， 還要考慮凝固路徑的影響。
關(guān)鍵字: 凝固路徑； 顯微偏析； 數(shù)值模擬
microsegregation parameters in Al-4.5%Cu alloy
（ 1. Joint Laboratory of Nanostructured Materials and Technology,
Nanjing University of Science and Technology, Nanjing 210094, China;
2. Department of Materials Science and Engineering,
Southeast University, Nanjing 210096, China）
Abstract: Effects of solidification path on microsegregation parameters after solidification at different locations in the ingot of Al-4.5%Cu alloy were studied by microsegregation forming simulation. The main kinetic effects that can influence microsegregation were accounted for in the modeling including secondary arm coarsening, solid-state back diffusion, primary tip undercooling and variable diffusion coefficients according to temperature. Deforming grids technology was applied for tracking the moving interfaces, iterative method was applied for resolving diffusion equation and solute balance equation. The simulation indicates that solid-state diffusion is controlled mainly by the solute diffusing velocity but not the local solidification time for Al-Cu system studied, and the microsegregation parameters are affected not only by local solidification time but also by solidification path.
Key words: solidification path; microsegregation; simulation
