The influence of solute segregation at grain boundaries on dislocation propagation in nanocrystalline Al alloys by molecular dynamics simulations

The interaction between solute atoms and dislocations is a key strengthening mechanism in aluminum alloys. However, the influence of solute segregation at grain boundaries (GBs) on dislocation propagation remains less understood, despite its potential significance in strengthening nanocrystalline materials. In this study, molecular dynamics simulations were carried out to investigate the effect of solute Cu and Mg segregation on dislocation propagation in polycrystalline and bicrystal Al models containing pre-inserted dislocations. The results show that solute segregation at GBs can reduce the contribution of dislocation mechanisms to total strain by pinning dislocation propagation along the GBs, thereby improving the strength of nanocrystalline Al alloys. Solute segregation increases the critical shear stress for initiating dislocation propagation at different temperatures and strain rates. The increase in pinning effect is related to solute segregation, which increases GB roughness and reduces the driving force for dislocation propagation. Compared to Mg, the segregation of solute Cu shows a stronger pinning effect on the dislocation propagation. This difference arises from their distinct chemical interactions and the resulting segregation behaviors. The interaction energy between Cu and dislocations exhibits greater fluctuation than that of Mg, resulting in a higher energy barrier for dislocation unpinning, and the clustering tendency of Cu can further amplify this unpinning barrier.