It was recalled that diffusion in nanocrystalline materials was often greatly enhanced, even beyond what was expected for a high density of equilibrated grain boundaries. It was proposed that this so-called anomalous diffusion could, in many cases, be due to short-circuit diffusion along triple junctions. Quantitative analysis showed that triple-junction diffusion could reasonably explain anomalies of several orders of magnitude. Therefore, previous suggestions of non-equilibrium grain boundary structures in nanocrystalline materials might not always be required in order to rationalize the anomaly.

Contribution of Triple Junctions to the Diffusion Anomaly in Nanocrystalline Materials. Y.Chen, C.A.Schuh: Scripta Materialia, 2007, 57[3], 253-6