A first-principles study of the β''-phase in Al-Mg-Si alloys

摘要: Al-Mg-Si alloys gain an increase in strength due to small precipitates of Mg and Si formed from the solid-solution phase, where maximum hardness arises a combination large number fully coherent Guinier-Preston (GP) 1 zones semi-coherent GP 2 (the β''-Mg5Si6 phase), both existing as needle-like structures. In present work we investigate nature bonding within equivalent bulk structure β''-phase, using density functional theory technique. particular presence covalent between calculated charge-density/transfer distributions structure. addition find residual Hellmann-Feynman forces on atoms, accordingly relax more symmetric terms geometry charge density. We also that converged is stable against atomic position perturbations break inversion mirror plane symmetries C2/m β''-phase. Finally face-centred-cubic array only atoms - candidate model for which β''-structure may be recovered by simple transformation subsequent relaxation.