Ab-initio study of the effect of rare-earth elements on the stacking faults of Mg solid solutions

The effects of RE (RE = Pr, Nd, Gd, Tb, Dy) solute atoms on four basal stacking faults of Mg solid solutions have been studied using density functional theory. From the generalized stacking fault energy surface, both stable and unstable stacking fault energies are reduced obviously with the addition of RE elements, and the effect becomes weak with increase of the atomic number of RE elements. Due to the decrease of fault energies of I2 stacking fault, the extended dislocation configuration tends to be stabilized and the ductility could also be improved by the addition of RE atoms. Then the deformation mechanisms are further studied by means of both the Rice and ZCT criterions. Finally, the electronic structure further reveals the underlying mechanisms for the effects of RE solutes on stacking faults of Mg solid solutions.

► The values of γis and γus of Mg-RE solid solutions are reduced obviously.
► The ductility of Mg-RE solid solutions could be improved.
► The dislocation configurations of Mg-RE solid solutions tend to be stabilized.
► RE elements are beneficial to promote the dissociation of dislocation into partials.