(上海大學(xué) 材料科學(xué)與工程學(xué)院 上海市現(xiàn)代冶金及材料制備重點(diǎn)實(shí)驗(yàn)室，上海 200072)
摘 要: 使用有限元耦合元胞自動(dòng)機(jī)模型預(yù)測(cè)水平單向凝固實(shí)驗(yàn)中Al-4.5%Cu(質(zhì)量分?jǐn)?shù))合金試樣的溫度場(chǎng)和微觀凝固組織。晶體形核和枝晶生長(zhǎng)動(dòng)力學(xué)模型分別采用Rappaz連續(xù)形核模型和Kurz-Giovanola-Trivedi(KGT)模型簡(jiǎn)化形式，基于純擴(kuò)散條件，采用KGT模型簡(jiǎn)化公式計(jì)算生長(zhǎng)參數(shù)。結(jié)果顯示：數(shù)值模擬可以較準(zhǔn)確地預(yù)測(cè)柱狀晶向等軸晶轉(zhuǎn)變(CET)位置和等軸晶晶粒尺寸，但因模擬未考慮晶核的運(yùn)動(dòng)，激冷等軸晶區(qū)的模擬有較大偏差。模擬和實(shí)驗(yàn)結(jié)果都證明過(guò)熱度顯著影響Al-Cu合金的凝固組織，過(guò)熱度低于20 ℃條件下可以獲得全等軸晶組織，否則會(huì)出現(xiàn)柱狀晶；過(guò)熱度50 ℃以上的試樣CET位置幾乎不發(fā)生變化。
關(guān)鍵字: Al-Cu合金；元胞自動(dòng)機(jī)；凝固過(guò)程；柱狀晶向等軸晶轉(zhuǎn)變；熱模擬
（Shanghai Key Laboratory of Modern Metallurgy and Materials Processing,
School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China）
Abstract:The temperature field and the grain structure of Al-4.5%Cu (mass fraction) alloy in horizontal directional solidification process were predicted using a cellular automaton (CA) coupled with finite-element (FE) model. The Rappaz model was adopted to calculate the nucleation. And the Kurz-Giovanola-Trivedi (KGT) model was used to describe the growth kinetics of dendritic tips. The growth parameters of Al-4.5%Cu alloy were calculated using simplified KGT formula, which was derived based on the pure diffusion condition. The results show that the position of the columnar to equiaxed transition (CET) and the size of equiaxed grains can be simulated reasonably. However, large deviation of the simulated result exists in the chill zone as the movement of nucleus is not considered. The simulated and experimental results prove that the superheat greatly influences the solidification microstructures of Al-Cu alloy. Full equiaxed grains can be obtained if superheat is lower than 20 ℃, otherwise columnar grains will be observed. When the superheat is above 50 ℃, the positions of CET are no longer changed.
Key words: Al-Cu alloy; cellular automaton; solidification process; columnar to equiaxed transition; thermal simulation
