Molecular Dynamics Simulation of Solution Strengthening of Si and Cu Atoms in Aluminum Alloy

For heat‐treatable aluminum alloys, solid solute elements play key role in material strengthening. Al–Mg–Si alloy is a typical heat‐treatable alloy; Cu and Si atoms are its main solid solution atoms. To reveal the strengthening mechanism, the interaction between the edge dislocations and the Cu and Si solute atoms of different concentration in aluminum matrix is investigated by molecular dynamics (MD) simulation. Results indicate that Cu atoms provide a more effective strengthening due to the stronger pinning effect. The increment of critical resolved shear stress (ΔCRSS) is a function of concentration of solid solute atoms. When more than two types of solid solution atoms coexist in matrix, the final increment of the ΔCRSS is determined by the interactive effects of the atoms instead of the direct sum of all items. The pinning of Cu solid solute atoms can lead to two Shockley partial dislocations merging to an edge dislocation.