Ab initio reappraisal of the dislocation-associated stacking faults in hcp titanium: a new dissociation mechanism

The ‹c + a› slip is a secondary slip system in hexagonal close-packed metals which is often activated when they undergo a c-axis deformation. The behaviour of the ‹c + a› screw dislocation remains unclear. Via ab initio calculations with an all atom all direction relaxation method, we find a stable 0.57 ‹c + a› stacking fault on {11 22} plane (π₂)and a stable nanotwinned 0.215 { 10 12} stacking fault on { 10 11} plane (π₁) in α-Ti. Based on these results, we propose a ‹c + a› screw dislocation dissociation mechanism which allows a split to three partials. This suggests a more complex ‹c + a› screw dislocation-related cross-slip mechanism.