Dislocation assisted phase separation: a phase field study

TL;DR

This study uses phase field modeling to reveal how dislocations affect phase separation mechanisms and morphologies in alloys, showing that dislocations can induce spinodal decomposition even outside traditional limits.

Contribution

It demonstrates the influence of dislocation dynamics on phase separation pathways and morphologies, providing new insights into defect-driven phase transformations in alloys.

Findings

Dislocations can enable spinodal decomposition outside the classical miscibility gap.

Concurrent nucleation and spinodal decomposition observed near intersecting dislocations.

Dislocation-driven morphology changes align with recent experimental observations.

Abstract

Defects play a key role in deciding the mechanisms and kinetics of phase transformations. In this paper, we show how dislocations influence phase separation in alloys with miscibility gap. Specifically, depending on the ratio of pipe mobility to bulk mobility, it is seen that even in a system with nominal compositions outside the spinodal limit, spinodal phase separation is possible. Surprisingly, phase separation through both nucleation and growth, and spinodal decomposition, is seen concurrently (for the case of intersecting dislocations). Finally, the prominent role played by dislocations in influencing the morphology of precipitates is explored. We show that these results agree qualitatively with recent experimental results in iron based systems obtained using Atom Probe Tomography (APT).