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

The grain growth processes are usually classified into two types. The first type is a self-similar coarsening process, which is called normal grain growth (NGG). The second type is called abnormal grain growth (AGG) and is characterized by the coarsening of a few grains at the expense of the surrounding matrix. Different mechanisms have been proposed for AGG, although the actual physical mechanism responsible for this phenomenon remains largely unknown. Dispersions of second phase particles are often used to inhibit NGG in polycrystalline metals. However, Hillert and also Humphreys predicted the condition where NGG does not occur and only AGG occurs by using the mean field analysis involving particle dispersions. In addition, Monte Carlo simulation on 'particle-assisted AGG' have been reported; however, the mechanism of the phenomenon has not been clarified yet. In this study, AGG due to the existence of the particles was reproduced by using 3D phase-field (PF) simulation. We particularly investigated the influence of dissolution rate of the particles on AGG intensity. Furthermore, we discussed characteristics of individual grains obtaining maximum size at the end of simulation. Our PF simulations revealed that not only the size superiority in the initial condition but also the "growth environment", that is, the average grain size of adjacent grains that changes sequentially during the simulation is important for enhancing the AGG. In order to extract the effects of the pinning particles the anisotropy in the interface properties was not considered in this manuscript.