(西北工業(yè)大學 材料科學與工程學院， 西安 710072)
摘 要: 基于離散格點形式的微擴散方程（Langevin方程）和非平衡自由能函數(shù)， 編制了引入原子間相互作用能變化的Al3Li（δ′）相沉淀原子層面計算機模擬程序。 該程序包容亞穩(wěn)區(qū)到失穩(wěn)區(qū)的全部溫度、 成分范圍和孕育期至粗化的全過程，可以處理與時間相關(guān)的過程問題。 開展了不同原子間相互作用勢下原子圖像、 序參數(shù)的計算機模擬， 進而探討了最近鄰原子相互作用能（W1）對有序相沉淀的影響機制。 發(fā)現(xiàn)過渡區(qū)合金形核前出現(xiàn)短暫的等成分有序化階段。探明隨W1的增大， 有序相沉淀的孕育期縮短，形核率增加， 合金有序化速度和原子簇聚速度加快， 在所研究的時間范圍內(nèi)達到的長程序參數(shù)和成分偏離序參數(shù)最大值增大。 隨W1的增大， 有序相的析出呈現(xiàn)出失穩(wěn)分解的特征。
關(guān)鍵字: 原子間相互作用勢； 沉淀； 原子圖像； 序參數(shù)； 計算機模擬
MA Liang, TANG Li-ying, ZHAO Yu-hong
（ School of Materials Science and Engineering,
Northwestern Polytechnical University, Xi′an 710072, China）
Abstract: An atomic-scale computer simulation program of δ′(Al3Li) based on the microscopic diffusion equation and non-equilibrium free energy was firstly worked out, which can be applied to process the problem relating with time. The precipitation mechanism of δ′ was investigated by simulating the atomic pictures and calculating the order parameters, etc, and the variation in precipitation mechanism with the nearest interchange interaction energy(W1), particularly the precipitation behavior of 12%Li in Al-Li alloys was interpreted. It is found that the precipitation incubation period of δ′ is shortened, the nucleation rate is increased, and the rate of ordering process and atom clustering are increased while the nearest interchange interaction energy increases. Within the studied time period, the maximum values of long range ordering parameter and composition deviation parameter increase with the nearest interchange interaction energy increasing. The precipitation of δ′ occurs either by a congruent ordering process followed by, or by a non-classical nucleation mechanism. With increasing W1, the precipitation of δ′ leans to decomposition.
Key words: interchange interaction energy; precipitation; computed microstructure; order parameters; computer simulation
