Electronic theory for solid-solution hardening and softening of dilute Al-based alloys: Elastic-moduli enhancement of Al-Li alloys.

Abstract

We discuss the characteristic solid-solution hardening and softening of Al-based fcc alloys using ab initio Korringa-Kohn-Rostoker augmented-spherical-wave electronic structure calculations. We choose the dilute Al-X alloy systems, X being Li, Be, Na, Mg, Ca, and Cu, which exhibit characteristic solid-solution hardening or softening; solute elements such as Li and Be significantly enhance the elastic moduli of Al-based alloys, while Mg and Ca decrease them strongly. On the other hand, a solute element like Cu has little effect on the elastic moduli. We will show that the characteristic solid-solution hardening or softening can be predicted correctly by total-energy calculations, and that they are correlated to the change in the lattice constants due to the solute atoms. Particular attention will be focused on the puzzling problem of solid-solution hardening of Al-Li alloys.