Tuning the creep rates of binary Al alloys by considering the effects of the stacking faults, alloying elements, and elastic moduli: a first-principles study

Abstract

Using first-principles calculations, the effects of intrinsic stacking faults, elastic moduli, and diffusivity on the creep rates of aluminum alloys Al–X (X = Sc, Nb, or Mo) have been investigated. The calculated stacking fault energies of dilute Al show stabilization in the case of Sc and destabilization in the case of Mo and Nb. Although all three impurities confer stiffer elastic properties, Sc appears to retain the ductility of Al but Mo and Nb push the system in the brittle regime. Also, Mo and Nb strongly increase the activation barrier to diffusion, leading to much reduced creep. The results indicate that Mo and Nb can be used in Al alloys to improve elastic properties and creep resistance but only at very low levels, before brittleness becomes an issue.