Simulation of coarsening in two-phase systems with dissimilar mobilities

• Published in: Computational materials science 2020-02, Vol.173 (C), p.109418, Article 109418
• Main Authors: Andrews, W. Beck, Voorhees, Peter W., Thornton, Katsuyo
• Format: Article
• Language: English
• Subjects: Coarsening; Materials Science; Morphology; Phase field modeling; Scaling
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2019.109418

[Display omitted] •Dissimilar mobilities and dimensionality (2D vs. 3D) both substantially affect coarsening kinetics and morphology.•High-mobility regions are discontinuous in 2D and continuous in 3D, leading to contrasting dynamics.•An analytical model is proposed that relates coarsening kinetics to morphology in 3D.•Effect of dissimilar mobilities on kinetics in 3D consists of change in average mobility offset by changes in morphology. In this work, we apply phase field simulations to examine the coarsening behavior of morphologically complex two-phase microstructures in which the phases have highly dissimilar mobilities, a condition approaching that found in experimental solid-liquid systems. Specifically, we consider a two-phase system at the critical composition (50% volume fraction) in which the mobilities of the two phases differ by a factor of 100. This system is simulated in two and three dimensions using the Cahn-Hilliard model with a concentration-dependent mobility, and results are compared to simulations with a constant mobility. A morphological transition occurs during coarsening of the two-dimensional system (corresponding to a thin film geometry) with dissimilar mobilities, resulting in a system of nearly-circular particles of high-mobility phase embedded in a low-mobility matrix. This morphological transition causes the coarsening rate constant to decrease over time, which explains why a previous study found lack of agreement with the theoretical t1/3 power law. Three-dimensional systems with dissimilar mobilities resulted in bicontinuous microstructures that evolve self-similarly, as determined by quantitative analysis of the interfacial shape distribution. Coarsening kinetics in three dimensions agreed closely with the t1/3 power law after the initial transient stage. A model is derived to explain a nearly-linear relationship between the coarsening rate constant and the variance of scaled mean curvature that is observed during this transient stage.