外势场对合金作用的离散法和连续法计算机模拟

【作者】 唐丽英；

【导师】 陈铮；

【作者基本信息】 西北工业大学 ， 材料学， 2004， 硕士

【摘要】 本文在国内首先编制了基于连续非经典形核理论的计算机模拟程序，可获得序参数、有序相半径、界面厚度、临界形核功等相关信息，并开展了与基于离散格点动力学模型的计算机模拟方法的比对研究。以Al-Li合金为客体，在国内外首先研究了原子间相互作用势对亚稳区合金和过渡区合金沉淀机制的影响，两种方法的主要研究结果吻合。 研究发现，随原子间相互作用势的增大，亚稳区合金和过渡区合金的δ′有序相的形核功减小，形核率增大。由离散格点模型得出：随原子间相互作用势的增大，有序相的尺寸和体积分数增大，其周围的无序基体浓度的下降加快，原子簇聚和有序化加快，化学计量比有序相长大加速。首次发现，原子间相互作用势的增大使亚稳区合金的相变机制向高浓度方向偏移，其中W₁单独作用影响程度最小，W₁、W₂协同作用影响程度最大。在沉淀的早期阶段，亚稳区合金的相界厚度基本不变，约为0.7nm；随时间的延长，过渡区合金的相界厚度由0.8nm左右逐渐减小到0.6nm左右，且减薄速度逐步变慢。更多还原

【Abstract】 In this paper, the computer simulation programs based on the continuum non-classical nucleation theory were firstly worked out, through which the order parameter, the radius of the ordered phase, the interface thickness and the critical nucleation energy were calculated. The comparison between the continuum theory and the discrete lattice dynamic model was carried out. The influences of the atomic interaction energy ( W1 and W2) to the precipitation mechanism of the Al-Li alloys in both metastable and intermediate regions were studied national and abroad for the first time. The results from the two methods are consistent.It was found that as the atomic interaction energy increased, the critical energy of the 8’ ordered phase decreased and the nucleation rate increased for the alloys in both metastable and intermediate regions. It was found from the discrete lattice dynamic model: as the atomic interaction energy increased, the sizes and volume fractions of the ordered phase raised, decline speed of composition in disordered matrix around the ordered phase was accelerated, the processes of clustering and ordering were accelerated, and the grow speed of the stoichiometric ordered phase was quicken. It was found for the first time that the increase of the atomic interaction energy made the precipitation mechanism of alloys in metastable region inclined to that of alloys with higher composition. The influence degree of W1 was the least and that of both W1 and W2 was the most. At the early stage of precipitation, the interface thickness of alloy in the metastable region was nearly unchanged, which was nearly 0.7nm; but that of alloys in the transient region decreased from 0.8nm to 0.6nm, and the decrease speeds become slower with time.更多还原