Grain-boundary sliding was an important deformation mechanism for elevated temperature forming processes. Molecular dynamics simulations were used to investigate the effect of solute atoms in near grain boundaries on the sliding of Al bicrystals at 477C. The threshold stress for grain-boundary sliding was computed for a variety of grain boundaries with different structures and energies. Without solute atoms, low-energy grain boundaries tend to exhibit significantly less sliding than high-energy grain boundaries. Simulation results showed that elements which tend to phase segregate from Al, such as Si, could enhance grain-boundary sliding in high-energy grain boundaries by weakening Al bonds and by increasing atomic mobility. In comparison, intermetallic forming elements, such as Mg, will form immobile Mg-Al clusters, decrease diffusivity, and inhibit grain-boundary sliding.

The Effect of Solute Atoms on Aluminum Grain Boundary Sliding at Elevated Temperature. N.Du, Y.Qi, P.E.Krajewski, A.F.Bower: Metallurgical and Materials Transactions A, 2011, 42[3], 651-9