The Effect of Solute Atoms on Aluminum Grain Boundary Sliding at Elevated Temperature

Grain boundary sliding (GBS) is an important deformation mechanism for elevated temperature forming processes. Molecular dynamics simulations are used to investigate the effect of solute atoms in near grain boundaries (GBs) on the sliding of Al bicrystals at 750 K (477 °C). The threshold stress for GBS is computed for a variety of GBs with different structures and energies. Without solute atoms, low-energy GBs tend to exhibit significantly less sliding than high-energy GBs. Simulation results show that elements which tend to phase segregate from Al, such as Si, can enhance GBS in high-energy GBs 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 GBS.