Effects of rare-earth elements on twinning deformation of Al alloys from first-principles calculations

Effects of rare-earth (RE = Ce, Dy, Er, Ho, La, Tb, and Yb) elements on twinning deformation of Al alloys are studied using first-principles calculations. The influence rules of RE atoms doped at the first nearest neighbor layer on the generalized planar-fault energy curves are analyzed, and the interaction energies of RE atoms in various atomic layers of stacking fault configurations are studied. On the basis of the improved twinning criterion formula and uniform distribution model, the influence rules of RE solute concentration on twinnability at the crack tip, at the grain boundary, and inside the grain of Al alloys are further analyzed. Results show that RE elements can evidently decrease the minimum energy barriers of dislocation nucleation and motion, and La and Ce atoms have significant effects on promoting dislocation nucleation and motion. Ce and La atoms can promote twinning deformation at the crack tip. Except for the La atom, the remaining RE atoms inhibit twinning deformation at the grain boundaries, and La atom at high concentrations is beneficial to promote twinning deformation at the grain boundaries. RE atoms (Dy, Er, Ho, La, Tb, and Yb) for twinning deformation inside Al alloy grains exhibit slight effect. Nevertheless, the Ce atom can greatly promote twinning deformation inside the grains when the solute concentration is in the range of 5%–7.1%, and the twinning ability decreases with the increase in solute concentration again. This work takes the lead in revealing the mechanism of twinning deformation by considering the interactions between RE atoms and generalized faults, which provides valuable guidance for exploiting high-performance Al–RE alloys.