| A new set of EAM potentials for Al, Mg, Al-Mg, and Al-Cu were developed using the force-matching method, a novel method for developing empirical potentials from ab initio forces plus experimental data. The optimized potentials gave good agreement with experimental data. We applied the potentials to interfacial segregation related phenomena in Al-Mg and Al-Cu alloys, including surface and grain-boundary segregation, grain-boundary fracture and grain-boundary diffusion.; Monte-Carlo simulations were performed to study Mg segregation at different low index surfaces of an Al alloy with 1 to 10% Mg. Surface enrichments of Mg of up to 80% are found and the segregation behavior is generally anisotropic. The results are compared with experiments and a set of discrete-lattice-plane calculations, based on the nearest-neighbor-broken-bond model corrected for strain energy. The effects of surface orientation, temperature, composition, and distance from surface were investigated.; Mg enrichment at various grain-boundaries of Al-10% Mg alloys at hot-working temperatures was studied with Monte-Carlo simulations. The Mg segregation level at grain-boundaries varied from 20% to 40%. First-principles calculations were performed and were found to generally agree with our empirical potential calculations. The segregation enrichment differences at different grain-boundary sites are explained in terms of atomic size and local hydrostatic stress. The segregation level varies strongly with (110) tilt boundaries from low to high angle while showing minimal variation with (100) twist boundaries. Segregation levels are found to have some correlation with grain-boundary energy. The effect of grain-boundary decohesion due to Mg segregation to grain-boundaries is found to be a modest (10 to 30%) reduction in fracture energy.; The segregation of Cu atoms at Al(110) {dollar}Sigma 111{dollar} and (001) {dollar}Sigma{dollar}5 tilt grain-boundaries was studied. Cu atoms were found to segregate to asymmetric sites at the {dollar}Sigma{dollar}11 boundary and form zig-zag planar aggregates at the interface. Segregation is dominated by atomic size and local hydrostatic stress. Cu atoms prefer to occupy the prime diffusion path sites at both grain-boundaries. Cu segregation raises that vacancy formation and diffusion activation energies at {dollar}Sigma{dollar}11 grain boundaries. |
