Phase-field Simulation of Abnormal Grain Growth due to the Existence of Second-phase Particles

Grain growth processes are usually classified into two types. The first is a self-similar coarsening process, which is known as normal grain growth, while the second is characterized by the coarsening of a few grains at the expense of the surrounding matrix, and is known as abnormal grain growth. Although different mechanisms have been proposed for abnormal grain growth, the actual physical mechanism responsible for this phenomenon remains largely unknown. To inhibit normal grain growth in polycrystalline metals, dispersions of second-phase particles are often used. Using mean field analysis involving particle dispersions, Hillert and Humphreys predicted the condition where only abnormal grain growth occurs. In addition, Monte Carlo simulations on particle-assisted abnormal grain growth have been reported; however, the mechanism for this phenomenon has yet to be clarified. In this study, the abnormal grain growth caused by dispersed particles was reproduced using three-dimensional phase-field (PF) simulations. In particular, we investigated the influence of the particle dissolution rate on the intensity of abnormal grain growth. Furthermore, we evaluated the characteristics of individual grains exhibiting the maximum grain size at the end of the simulation. Our PF simulations revealed that size superiority under the initial condition is important for enhancing abnormal grain growth, as is the "growth environment," i.e., the average grain size of adjacent grains that changes sequentially during the simulation. To deduce the effects of the pinning particles, the anisotropy in the interface properties was not considered in this study.