Scale bridging description of coherent phase equilibria in the presence of surfaces and interfaces

TL;DR

This paper develops a scale-bridging theory to describe how elastic effects at surfaces and interfaces influence phase separation, significantly reducing solubility limits and promoting phase formation near free surfaces in metals.

Contribution

It introduces a novel theoretical framework that captures elastic coherency effects on phase equilibria at surfaces, applicable to materials like nickel, iron, and niobium.

Findings

Solubility limits are reduced by up to two orders of magnitude at room temperature near free surfaces.

Elastic effects favor phase separation at surfaces even without external stresses.

The theory provides a solubility modification factor linking elastic effects to ab initio calculations.

Abstract

We investigate phase separation including elastic coherency effects in the bulk and at surfaces and find a reduction of the solubility limit in the presence of free surfaces. This mechanism favours phase separation near free surfaces even in the absence of external stresses. We apply the theory to hydride formation in nickel, iron and niobium and obtain a reduction of the solubility limit by up to two orders of magnitude at room temperature in the presence of free surfaces. These effects are concisely expressed through a solubility modification factor, which transparently expresses the long-ranged elastic effects in a terminology accessible e.g. to ab initio calculations.