Phase-field modeling of equilibrium precipitate shapes under the influence of coherency stresses

TL;DR

This paper introduces a novel phase-field model to study equilibrium precipitate shapes influenced by coherency stresses and anisotropies, extending previous sharp interface methods and exploring complex shape bifurcations.

Contribution

A new diffuse interface phase-field approach is developed to analyze precipitate shapes under elastic and interfacial anisotropies, overcoming limitations of sharp interface models.

Findings

Reproduced shape-bifurcation diagrams for pure dilatational misfit.

Extended models to include interfacial energy anisotropy with various strengths.

Analyzed effects of misfit strain asymmetry on precipitate morphologies.

Abstract

Coherency misfit stresses and their related anisotropies are known to influence the equilibrium shapes of precipitates. Additionally, mechanical properties of the alloys are also dependent on the shapes of the precipitates. Therefore, in order to investigate the mechanical response of a material which undergoes precipitation during heat treatment, it is important to derive the range of precipitate shapes that evolve. In this regard, several studies have been conducted in the past using sharp interface approaches where the influence of elastic energy anisotropy on the precipitate shapes has been investigated. In this paper, we propose a diffuse interface approach which allows us to minimize grid-anisotropy related issues applicable in sharp-interface methods. In this context, we introduce a novel phase-field method where we minimize the functional consisting of the elastic and surface energy contributions while preserving the precipitate volume. Using this method we reproduce the shape-bifurcation diagrams for the cases of pure dilatational misfit that have been studied previously using sharp interface methods and then extend them to include interfacial energy anisotropy with different anisotropy strengths which has not been a part of previous sharp-interface models. While we restrict ourselves to cubic anisotropies in both elastic and interfacial energies in this study, the model is generic enough to handle any combination of anisotropies in both the bulk and interfacial terms. Further, we have examined the influence of asymmetry in dilatational misfit strains along with interfacial energy anisotropy on precipitate morphologies.