Atomistic Simulations Reveal the Need to Reassess Standard Thermodynamic Models of Coherent Precipitates

TL;DR

Atomistic simulations of Fe-Cr precipitates show that common assumptions in thermodynamic models are invalid even at low misfit and supersaturation, indicating a need to revise current precipitation modeling approaches.

Contribution

This study challenges standard assumptions in thermodynamic modeling of coherent precipitates using atomistic simulations, revealing their limitations.

Findings

Elastic effects cannot be neglected even with small lattice misfit.

Size effects are significant at low supersaturation levels.

Higher-order effects become important at large precipitate sizes.

Abstract

Accurate models of precipitation kinetics are essential to control and design structural materials. These models are highly sensitive to the thermodynamic description of precipitates. We use atomistic simulations of a model Fe-Cr system to assess two commonly used assumptions in the thermodynamic modeling of coherent precipitates: that elastic effects can be neglected for systems with a small lattice misfit and that size effects can be neglected for low levels of supersaturation. We find that these assumptions cannot be maintained for an accurate description of interfacial equilibrium, even when lattice misfits are below 1 % and supersaturation values are below 1 %. Additionally, we find a surprising trend at large precipitate radii that suggests the importance of higher-order effects that are commonly neglected. The results and insights from this study highlight the need to revisit current approaches in modeling solid-state precipitation.