Diffusion in the Presence of Twin Boundaries

In this paper, four examples from the literature are introduced in which the presence of high density of twin boundaries could explain an anomalous diffusion behavior. (i) In the case of the grain boundary (GB) self-diffusion in nickel, leakage from the random GBs to considerably high fraction of deformation and/or annealing twins in the samples studied can be a reason for the diverse literature values of activation enthalpy. The diffusion model including participation of two types of GBs is essential for data evaluation. (ii) Segregation of Ge atoms with negligible solubility to twin boundaries and diffusion in both type A and type AB transition regime can clarify the unusual 71Ge diffusion in the Mg alloys. (iii) Anomalous diffusion of gold in polycrystalline silicon presented in the literature was discussed here. Because profiles corresponding to type AB transition regime were detected, transition from type B to type A diffusion regime could be an alternative explanation of the anomaly. (iv) Effective diffusion of the 63Ni tracer in the presence of unidirectional defects in single-crystalline β-tin might be a simple reason for the uncommon features published earlier: low activation enthalpy, high diffusion anisotropy and values of the extrapolated solid-state Ni diffusion coefficients above those in the Sn liquid phase.