Nominal vs. actual supersaturation of solutions

TL;DR

This paper distinguishes between actual and nominal supersaturation in solutions by incorporating heterophase fluctuations into Classical Nucleation Theory, validated through simulation data on aluminum alloys.

Contribution

It introduces an algebraic equation linking actual and nominal supersaturation, accounting for interface energy and temperature effects, extending classical nucleation models.

Findings

The model accurately predicts nucleation behavior in aluminum alloys.

Heterophase fluctuations significantly affect supersaturation calculations.

Validation against simulation data confirms the model's applicability.

Abstract

Following the formalism of the Classical Nucleation Theory beyond the dilute solution approximation, this paper considers a difference between the actual solute supersaturation (given by the present-to-saturated solute activity ratio) and the nominal supersaturation (given by the present-to-saturated solute concentration ratio) due to formation of subcritical transient solute clusters, called heterophase fluctuations. Based on their distribution function, we introduce an algebraic equation of supersaturation that couples the nominal supersaturation of a binary metastable solution with its actual supersaturation and a function of the specific interface energy and temperature. The applicability of this approach is validated by comparison to simulation data [E. Clouet et al., Phys. Rev. B \textbf{69}, 064109 (2004)] on nucleation of Al$_{3}$Zr and Al$_{3}$Sc in model binary Al alloys.