  Grain boundary engineering via dopant segregation can dramatically change the
properties of a material. For metallic systems, most current studies concerning
interfacial segregation and subsequent transitions of grain boundary structure
are limited to binary alloys, yet many important alloy systems contain more
than one type of dopant. In this work, hybrid Monte Carlo/molecular dynamics
simulations are performed to investigate the behavior of dopants at interfaces
in two model ternary alloy systems: Cu-Zr-Ag and Al-Zr-Cu. Trends in boundary
segregation are studied, as well as the propensity for the grain boundary
structure to become disordered at high temperature and doping concentration.
For Al-Zr-Cu, we find that the two solutes prefer to occupy different sites at
the grain boundary, leading to a synergistic doping effect. Alternatively, for
Cu-Zr-Ag, there is site competition because the preferred segregation sites are
the same. Finally, we find that thicker amorphous intergranular films can be
formed in ternary systems by controlling the concentration ratio of different
solute elements.
