The Department of Physics and Astronomy invites all to a colloquium featuring Dr. Sergiy V. Divinski, Institute of Materials Physics, University of Münster, Germany. Dr. Divinski will present his talk, “Grain boundary phase transitions studied by radiotracer diffusion”, Tuesday, November 1 at 4:10 p.m. in Webster 17.
Meet for refreshments before the lecture at 3:45 – 4:10 p.m. in the foyer on floor G above the lecture hall.
Abstract: Grain boundary diffusion of (_^110m)”Ag” in Cu near Σ5 bicrystals is measured parallel and perpendicular to the (001) misorientation axis in both, C and B kinetic regimes after common Harrison’s classification. As a result, the grain boundary diffusion coefficients, D_gb, for a single grain boundary in a true dilute limit of the solute concentration are determined in the C kinetic regime and the values of triple products P=s∙δ∙D_gb are measured in the B regime (here s and δ are the segregation factor and the diffusional grain boundary width, respectively). A significant anisotropy of the grain boundary diffusion is established which disappears at the temperatures above 823 K. This temperature corresponds also to a kink in the Arrhenius temperature dependence of the triple product. The phenomenon is discussed in term of a special-to-general transition of the grain boundary structure.
The anisotropy of the product s∙δ for a single grain boundary is determined. The effect of non-linear segregation on Ag diffusion in the Cu bicrystal is elucidated via controlled variation of the total amount of the applied tracer material. Moreover, grain boundary phase transitions induced by solute segregation are discussed for the systems Cu-Bi and Al-Ga.
