Solid solution decomposition and Guinier-Preston zone formation in Al-Cu alloys: A kinetic theory with anisotropic interactions

TL;DR

This paper develops a kinetic theory model incorporating first-principles interactions to study the decomposition and microstructure evolution in Al-Cu alloys, revealing temperature-dependent transitions in precipitate morphology and zone formation.

Contribution

It introduces a kinetic model that accounts for chemical and strain effects, providing new insights into the microstructure evolution in Al-Cu alloys.

Findings

Decomposition involves multiple stages with GP zone formation.

Transition from GP1 to GP2 zones is kinetically driven.

Precipitate morphology shifts from platelets to equiaxial with temperature.

Abstract

Using methods of statistical kinetic theory parametrized with first-principles interatomic interactions that include chemical and strain contributions, we investigated the kinetics of decomposition and microstructure formation in Al-Cu alloys as a function of temperature and alloy concentration. We show that the decomposition of the solid solution forming platelets of copper, known as Guinier-Preston (GP) zones, includes several stages and that the transition from GP1 to GP2 zones is determined mainly by kinetic factors. With increasing temperature, the model predicts a gradual transition from platelet-like precipitates to equiaxial ones and at intermediate temperatures both precipitate morphologies may coexist.