A phase-field approach for modeling equilibrium solute segregation at the interphase boundary in binary alloys

TL;DR

This paper introduces a phase-field model for simulating solute segregation at interphase boundaries in binary alloys, capturing thermodynamics, interfacial energies, and mass transport, with analytical solutions and computational analysis.

Contribution

The paper presents a novel phase-field modeling framework that accurately describes equilibrium solute segregation at interphase boundaries in binary alloys, including analytical solutions and parameter analysis.

Findings

Model captures bulk thermodynamics and interfacial free energies.

Segregation isotherms relate alloy composition and model parameters.

Model aligns with Gibbs adsorption equation and can be compared with experiments.

Abstract

A number of experimental and theoretical findings in age hardening alloys suggest that specific solute elements preferentially segregate to and reduce the energy of the interphase boundary (IB). This segregation mechanism can stabilize the precipitation microstructure against coarsening, allowing higher operating temperatures in structural applications. Herein, we present a phase field model of solute segregation to IBs that separate matrix and precipitate phases in binary alloys. The proposed modeling framework is capable of capturing bulk thermodynamics and interfacial free energies, while also accounting for various mass transport mechanisms. Analytical equilibrium solutions of one-dimensional systems are presented, and excess IB quantities are evaluated independent of the Gibbs dividing surface convention. With the aid of the parallel tangent construction, IB segregation isotherms are established in terms of the alloy composition and the model parameters describing the free energy functions. Under the regular solution approximation, computational studies elucidating the dependence of the IB energy and segregation levels on temperature and free energy model parameters are presented. We show that the model is consistent with the Gibbs adsorption equation; therefore, it is possible to compare the adsorption behavior predicted by the model parameters with experiments and atomistic simulations. Future work on extending the model to ternary alloys, and incorporating the effect of elastic interactions on IB segregation is expected.