ABSTRACT The topological structure of the recently developed MultiParticle (MP) model of Ostwald ripening based on direct pairwise interactions has been extended to describe the coarsening of grain-boundary (GB) precipitates by introducing a 2D diffusion geometry. In agreement with previous studies in the literature, the model predicts that the mean radius grows proportionally to t1/4. The analysis carried out in this work originates from the observation that in some cases the t1/3 kinetics, typical of a process controlled by bulk diffusion, is recovered also in systems where almost all particles are located on grain boundaries. In order to investigate this discrepancy, an ideal system with small volume fraction of second phase (0.05) where all precipitates are on GBs has been considered. By calculating the ratio between the coarsening rate predicted when the system is controlled by GB diffusion and that of the same system controlled by bulk diffusion it is found that, even by imposing a diffusion coefficient at GBs 100 times that in the bulk, GB diffusion dominates only when the mean particle size is below a limiting value. Since the system is anyway undergoing coarsening, eventually the bulk diffusion mechanism will prevail. This provides a possible explanation of the experimental results. For the sake of completeness, a kinetic equation describing the true 2D Ostwald ripening of island-like cylindrical particles within the framework of the MP model is also developed. As expected, it is characterised by a t1/3 coarsening law.

中文翻译：

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晶界析出物的粗化动力学：基于奥斯特瓦尔德熟化多对相互作用模型的再分析

摘要 最近开发的基于直接成对相互作用的奥斯特瓦尔德熟化多粒子 (MP) 模型的拓扑结构已扩展到通过引入 2D 扩散几何来描述晶界 (GB) 沉淀物的粗化。与文献中先前的研究一致，该模型预测平均半径与 t1/4 成比例增长。在这项工作中进行的分析源于以下观察：在某些情况下，t1/3 动力学，这是由体扩散控制的过程的典型特征，在几乎所有粒子都位于晶界的系统中也可以恢复。为了研究这种差异，已经考虑了具有小体积分数的第二相 (0.05) 的理想系统，其中所有沉淀物都在 GB 上。通过计算当系统由 GB 扩散控制时预测的粗化率与由体扩散控制的同一系统的粗化率之间的比率发现，即使在 GBs 处施加 100 倍于体中的扩散系数，GB 扩散仍占主导地位仅当平均粒径低于极限值时。由于系统无论如何都在经历粗化，最终体扩散机制将占上风。这为实验结果提供了可能的解释。为了完整起见，还开发了描述 MP 模型框架内岛状圆柱形颗粒的真实 2D Ostwald 成熟的动力学方程。正如预期的那样，它的特点是 t1/3 粗化规律。