(a) Schematic showing the temperature dependent free energy of a grain boundary with a fixed misorientation and grain boundary plane exhibiting 2 different complexions. The schematic also highlights the general experimental approach where samples are pre-annealed at temperatures above and below a transition temperature and then diffusion anneals are subsequently performed at lower temperatures in order to approximate Δγ. (b) Schematic following Ref. 26 depicting the general concept and assumptions used in the Borisov model to relate γ to diffusivity.
Schematic describing the predictions of the Borisov model for (a) a decrease in ΔHb at fixed S and ν* and (b) an increase in ΔSb at fixed H and ν*.
(a) Rutherford backscattering spectra for Cu-Ni calibration samples of different nominal composition, (b) the calibration curve determined from the combined results of SIMS and RBS.
Chemical tracer profiles for constant source Cu diffusion into the (a) 773 K and (b) 1173 K pre-annealed Ni-Bi sample at 473 K, 423 K, 373 K, and 300 K. Note: 523 K and 473 K diffusion profiles of the 973 K pre-annealed Ni-Bi sample were obtained using 5 nm Cu (instantaneous) diffusion source.
Chemical tracer profiles for constant source Au diffusion into the (a) 773 K and (b) 1173 K pre-annealed Cu-Bi sample at 473 K, 423 K, 373 K, and 300 K.
Dependence of diffusivity on inverse diffusion temperature in (a) Cu-Bi and (b) Ni-Bi samples.
In-plane STEM micrographs of the microstructures after the pre-annealing for (a) Ni-Bi at 573 K, (b) Ni-Bi at 973 K, (c) Cu-Bi at 773 K, and (d) Cu-Bi at 1173 K. Note: the bright contrasts in the grain of (d) are primarily from occluded Bi particles.
(a) HAADF-STEM image of Cu annealed with Bi at 1173 K highlighting a region where Bi has been occluded in the Cu grain, and (b) a TEM micrograph of the occluded Bi nanoparticles that are distinguished by the Moire fringes.
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