Mechanism on Material Strengthening of Metastable Precipitate and Edge Dislocation in Al–Mg–Si Alloy

Abstract

The metastable precipitate β″ plays a key role in material strengthening in Al–Mg–Si alloys. To investigate the mechanism on material strengthening of metastable precipitates, the interaction between β″ metastable precipitates and edge dislocations is studied using molecular dynamics. It is indicated in the results that the precipitate can be overcome by shearing without the formation of Orowan loops in case of smaller precipitate sizes. By increasing the temperature and reducing the shear strain rate, the critical resolved shear stress (CRSS) can be decreased. Larger precipitate sizes can lead to higher CRSS due to larger interaction area. Shear deformation can be clearly found on the precipitate when dislocations interact with the precipitate. When newly generated dislocations further interact with the sheared precipitate, the strengthening can be reduced due to the smaller cut width. This is the reason that strain hardening decreases with the increase of plastic deformation in macro scale.