| Abstract Scope |
The triple junctions (TJs), where three grains meet in a polycrystal, represent line defects with enormous crystallographic variability. In the finest nanocrystalline materials with grain sizes below about 10-15 nm— a range where many commercial nanocrystalline materials lie— TJs are the volumetrically dominant defect type. This talk will review our recent efforts to understand the innate energetics of TJs, and how those energetics influence alloy configuration in nanomaterials. First, we develop a grain-size-scaling approach to compute polycrystalline-average TJ energies, which are generally negative (favorable) in pure metals, and offset the penalty of their associated grain boundaries. We proceed to evaluate the solute segregation behavior of TJs, which have distinct spectra of atomic sites for segregation in both substitutional and interstitial alloys, as compared with GBs. We show how this leads to new opportunities for structural stabilization and the design of nanocrystalline alloys. |