Effects of alloying elements on deformation and fracture; First-principles approach to element strategy

Tsuru, Tomohito   ; Somekawa, Hidetoshi*; Itakura, Mitsuhiro  ; Yamaguchi, Masatake   

Mg alloys have great potential for the next generation of structural materials. Widespread application, however, has been limited because of a key weakness stemming from their hexagonal-close-packed (hcp) crystal structure. Their elongation-to-failure is extremely low due to the strong anisotropy of plastic deformation and decohesion of twin boundary in HCP metals. Recently it has been known that solute atoms alter the plastic deformation dramatically. However, the detailed mechanism is still unclear. We investigated the dislocation core structure of some typical HCP metals and the effects of solute atoms on dislocation core structure and motion in Mg especially. An initial atomic configuration is constructed by solving for the displacement field of the dislocation dipole within a periodic continuum linear elasticity theory. DFT calculations were carried out to explore the stable dislocation core structure.