Competition between prismatic and basal slip in hexagonal titanium-aluminum alloys with short-range order

International audiencePlasticity of hexagonal titanium-aluminum alloys depends on the solute concentration and the order state of Al atoms. Development of short-range order (SRO) modifies Al strengthening and impacts the competition between prismatic and basal slip modes. Using ab initio calculations, we study the interaction of a screw dislocation with isolated Al atoms and Al pairs in a hcp Ti existing in short-range ordered Ti-Al alloys. Calculated activation energies reveal pronounced hardening caused by Al addition for both slip systems, which become competitive. This hardening is enhanced for Al pairs, resulting in a reduced plastic anisotropy of Ti-Al alloys with SRO