SOLUTE-ATOM SEGREGATION AT SYMMETRICAL TWIST BOUNDARIES STUDIED BY MONTE-CARLO SIMULATION

Detailed Monte Carlo simulations are performed of solute-atom segregation at (002) twist boundaries in the Au-Pt system at 850 K; the particular single-phase bicrystal alloys studied are Pt-1 at% Au and Au-1 at% Pt. The emphasis in this paper is on studying the distribution of solute atoms at low-angle boundaries. For the Pt-1 at% Au alloy the distribution of sites enhanced in the solute species Au is found to form a bipyramid based on the square cells of the orthogonal primary grain boundary screw dislocations. In the case of the Au-1 at% Pt alloy the solute species Pt is found to be depleted and it also forms a similar bipyramidal pattern. The Gibbsian interfacial excesses of Au and Pt are found to be positive and negative, respectively, for the Pt-1 at%. Au and Au-1 at% Pt bicrystal alloys. The absolute values of these Gibbsian interfacial excesses both increase with increasing twist angle.