SOLUTE-ATOM SEGREGATION AT (002) TWIST BOUNDARIES IN DILUTE NI-PT ALLOYS - STRUCTURAL CHEMICAL RELATIONS

Monte Carlo simulations, utilizing embedded atom method (EAM) potentials, are used to investigate solute-atom segregation behavior at symmetrical (002) twist boundaries, at T = 850 K, in Pt-3 at.% Ni and Ni-3 at.% Pt alloys. The results show that, unlike the previously investigated Au-Pt system, the boundaries are enhanced in solute atoms on both sides of the phase diagram. For low-angle boundaries on the Pt-rich side the atomic sites enhanced in solute concentration are arranged in hourglass-like structures centered on the square grid of primary grain boundary dislocations. While for the same boundaries on the Ni-rich side the atomic sites enhanced in solute concentration are located in bipyramidal regions based on the square cells of the same grain boundary dislocations. Thus, the atomic sites that are enhanced on one side of the phase diagram are not affected on the other side and vice versa.