Segregation of Sc and its effects on the strength of Al Σ5 (210) [100] symmetrical tilt grain boundary

Abstract

Full investigation has been made into the Sc segregation behavior and its influence on the Al Σ5 (210) [100] symmetrical tilt grain boundary (GB) through systematic first-principles calculations. The preferential sites and sequence for the substitution of Sc for Al in the GB were determined, so were the separation energy and tensile strength of the GB after the addition of Sc. The distribution of charge density and the change in bond lengths were analyzed to reveal the underlying mechanism. The calculation results demonstrate that Sc atoms have a strong tendency to segregate to the Al Σ5 (210) [100] GB, substituting all the Al atoms along the GB. With the introduction of Sc atoms, it's found that most of bond lengths in the GB become larger, especially in the doped side; the charge density between two grains increases obviously and the area nearly empty of electrons shrinks substantially and disappears in the end; both of the separation energy and tensile strength for the GB get improvement. The study conclusions suggest that the enhancement of fracture resistance for Al series alloys by adding Sc results mainly from the GB strengthening which is obtained through the Sc segregation.