Solute effects on ß-sn grain boundary energy and shear stress

The excess enthalpy and shear strain behavior of the β-Sn d101T grain boundary containing various amounts of Ag and Cu solute atoms was investigated using molecular simulation. An increase in either type of solute at the interface lowers the excess enthalpy of the grain boundary. The enthalpies of segregation for both solute types are computed as the slope of excess enthalpy of the grain boundary per area versus interfacial solute concentration per area. For Ag, ΔH^SEG. 0:64d9T eV=atom, and for Cu, ΔH^SEG. 0:45d8T eV=atom, indicating a preference for grain boundary segregation. These results agree with other simulation work that attributes a larger decrease in grain boundary energy to a solute with a larger atomic radius. A d301T special boundary of β-Sn was also investigated and found ΔH^SEG. 0:12d9T eV=atom for Ag and ΔH^SEG. 0:06d9T eV=atom for Cu. Statistically, this shows the possibility for excess enthalpy increase when Cu is present at the d301T boundary. Under constant shear strain, addition of solute lowers the yield stress of the boundary. For larger strain, yield stress levels are maintained when compared with the pure case. This indicates that the solute addition hinders sliding at the d101T interface. An interesting structural transition that occurs in the pure d101T boundary at high temperature was also explored.