First-principles study on solute-basal dislocation interaction in Mg alloys

To better understand the influence of alloying elements on the mechanical properties of Mg-X (Al, Sn, Ca, Y, Sc, Er, Gd, and Nd) binary alloys, the local interactions between the solute atoms and basal screw dislocation cores were investigated using first-principles calculations. It is revealed that Rare Earth (Y, Sc, Er, Gd, and Nd) and Ca solute atoms can hinder the dissociation behavior of the full basal dislocation core to different extents. Moreover, Y, Sc, and Er tend to stabilize the perfect Burgers vector of basal dislocations. Furthermore, Sn, Y, and Nd were selected to access the interactions between solute atoms and partial dislocations. It is found that Y and Nd can alter the structure of partial dislocation and reduce the width of the stacking fault at specific locations. By comparison, Al and Sn solutes slightly influence the width of the stacking fault. The energies of relaxed basal dislocation cores decorated by Rare Earth and Ca are significantly lower than those decorated by Al and Sn, which suggests that a stronger binding is present between Rare Earth elements, Ca solute atoms, and basal dislocation cores. Moreover, non-planar basal dislocation cores would be induced by Rare Earth solutes. Finally, the physical factors of alloying elements influencing dislocation core structures and the implications of the diverse geometries of dislocation cores to mechanical properties of Mg alloys are discussed.