Precipitate-Induced Dynamic Strain Aging and Its Effect on the Strain Rate Sensitivity of Precipitation Hardened Aluminum Alloys

TL;DR

This study uses atomistic simulations, kinetic Monte Carlo, and analytical modeling to understand how precipitate-induced dynamic strain aging affects strain rate sensitivity in aluminum alloys, revealing a mechanistic origin for low strain-rate sensitivity.

Contribution

It introduces a multi-scale modeling approach combining atomistic, kinetic, and analytical methods to explain strain rate sensitivity in precipitation-hardened aluminum alloys.

Findings

Predicted low strain-rate sensitivity consistent with experiments.

Identified dislocation-precipitate interaction kinetics as the origin of low sensitivity.

Provided a mechanistic understanding of dynamic strain aging effects.

Abstract

We examine precipitate-induced dynamic strain aging in precipitation-hardened Al-Cu alloys by combining atomistic simulations, kinetic Monte Carlo, and analytical rate theory. Atomistic simulations were used to characterize (1) the energetics of nearest neighbour Cu<->Al exchanges at dislocation - precipitate junctions and (2) the subsequent change in obstacle strength. For robustness, the simulations were performed with two distinct interatomic potentials. The resulting catalog of local Cu-Al exchange events was used as input for a kinetic Monte Carlo model of the time-dependent evolution of obstacle strength during dislocation pinning at the precipitate. The predicted strengthening kinetics were then embedded in an analytical dynamic strain aging model to predict the strain-rate sensitivity parameter. On the whole, the modeling predicts a low strain-rate sensitivity across a broad range of intermediate quasi-static strain rates, consistent with experimental observations for precipitate-strengthened alloys. The results therefore identify a mechanistic origin of the low strain-rate sensitivity in precipitation hardened aluminum alloys, emerging directly from the kinetics of dislocation-precipitate interactions when nearest neighbour Cu<->Al exchanges are considered.