Dislocation dynamics prediction of the strength of Al-Cu alloys containing shearable $\theta''$ precipitates

TL;DR

This paper uses dislocation dynamics simulations combined with experimental data to predict the strength of Al-Cu alloys with $ heta''$ precipitates, accurately modeling dislocation-precipitate interactions and optimizing alloy strength.

Contribution

It introduces a comprehensive dislocation dynamics approach integrating atomistic and microscopy data to predict alloy strength considering precipitate shearability and distribution.

Findings

Simulation predictions agree with experimental measurements.

Optimal alloy strength occurs with $ heta''$ precipitates around 40 nm.

Dislocation-precipitate interactions depend on precipitate shearability.

Abstract

The critical resolved shear stress of an Al 4 wt. \% Cu alloy containing a homogeneous distribution of $\theta''$ precipitates was determined by means of dislocation dynamics simulations. The size distribution, shape, orientation and volume fraction of the precipitates in the alloy were obtained from transmission electron microscopy observations while the parameters controlling the dislocation/precipitate interactions (elastic mismatch, transformation strains, dislocation mobility and cross-slip probability, etc.) were calculated from atomistic simulations. The precipitates were assumed to be either impenetrable or shearable by the dislocations, the latter characterized by a threshold shear stress that has to be overcome to shear the precipitate. The predictions of the simulations in terms of the critical resolved shear stress and of the dislocation/precipitate interaction mechanisms were in good agreement with the experimental results. It was concluded that the optimum strength of this alloy is attained with a homogeneous distribution of $\theta''$ precipitates whose average size ($\approx$ 40 nm) is at the transition between precipitate shearing and looping. Overall, the dislocation dynamics strategy presented in this paper is able to provide quantitative predictions of precipitate strengthening in metallic alloys.