Novel cross-slip mechanism of pyramidal screw dislocations in magnesium

Itakura, Mitsuhiro  ; Kaburaki, Hideo; Yamaguchi, Masatake   ; Tsuru, Tomohito   

Dislocations in close packed metals usually dissociate into a planar shape and their slip is confined in the corresponding slip planes. Cross-slip usually requires transformation of the planar dislocation core into a perfect dislocations, which requires high activation energy. Using an extensive DFT calculations, we have found a notable exception to this conventional view. The pyramidal c+a screw dislocation in Mg consists of two partial dislocations connected by a stacking fault, and the stacking fault can migrate perpendicular to the plane by atom shuffling, enabling the dislocation to cross-slip without transforming into a perfect dislocation.