Multiscale modelling of precipitation hardening in Al-Cu alloys: dislocation dynamics simulations and experimental validation

TL;DR

This study combines dislocation dynamics simulations with experimental validation to understand how precipitates strengthen Al-Cu alloys, revealing the dominant role of transformation strains in hardening.

Contribution

It introduces a multiscale approach integrating atomistic, simulation, and experimental data to analyze dislocation-precipitate interactions in Al-Cu alloys.

Findings

Transformation strains are the primary contributor to precipitation hardening.

Simulation predictions match experimental critical shear stress measurements.

Dislocation bow-out (Orowan mechanism) also significantly contributes to hardening.

Abstract

The mechanisms of dislocation/precipitate interactions were analyzed in an Al-Cu alloy containing a homogeneous dispersion of $\theta'$ precipitates by means of discrete dislocation dynamics simulations. The simulations were carried out within the framework of the discrete-continuous method and the precipitates were assumed to be impenetrable by dislocations. The main parameters that determine the dislocation/precipitate interactions (elastic mismatch, stress-free transformation strains, dislocation mobility and cross-slip rate) were obtained from atomistic simulations, while the size, shape, spatial distribution and volume fraction of the precipitates were obtained from transmission electron microscopy. The predictions of the critical resolved shear stress (including the contribution of solid solution) were in agreement with the experimental results obtained by means of compression tests in micropillars of the Al-Cu alloy oriented for single slip. The simulations revealed that the most important contribution to the precipitation hardening of the alloy was provided by the stress-free transformation strains followed by the solution hardening and the Orowan mechanism due to the bow-out of the dislocations around the precipitates.