Atomistic Simulation Study of Mechanical Deformation of Al-Mg-Si Alloys

Aluminum alloys have been attracting significant attention. Especially Al-Mg-Si alloys can exhibit an excellent balance between strength and ductility. Deformation mechanisms and microstructural evolution still remain challenging issues in these materials. Accordingly, in an effort to describe how the type of phase influence mechanical behavior of Al/Mg/Si alloys, in this paper atomic simulations are performed to investigate the uniaxial compressive behavior of Al-Mg-Si ternary phases. The compression is at the same strain rate (3.10(10) s(-1)); using Modified Embedded Atom Method (MEAM) potential to model the deformation behavior. From these simulations, we acquire the total Radial Distribution Function; enabling us to acquire the stress-strain responses to describe the elastic and plastic behaviors of GP-AlMg4Si6, U2-Al4Mg4Si4 and beta-Al3Mg2Si6 phases. For a detailed description of which phase influence hardness and ductility of these alloys; the mechanical properties are determined and presented using molecular dynamics simulation. These stress-strain curves obtained show a rapid increase in stress up to a maximum followed by a gradual drop when the specimen fails by ductile fracture. From the simulation results, it was found that GP-AlMg4Si6 & U2-Al4Mg4Si4 phases are brittle under uniaxial compressive loading, while beta-Al3Mg2Si6 phase is very ductile under the same stress conditions. The engineering stress-strain relationship suggests that beta-Al3Mg2Si6 phase have high elasticity limit, ability to resist deformation and have the advantage of being highly malleable. Molecular dynamics software LAMMPS was used to simulate and build the Al-Mg-Si ternary system.