Triple junction segregation in nanocrystalline multilayers

Triple junctions (TJ's), topologically required linear defects of grain boundary structure, are suggested to control the behavior of nanocrystalline material. However, measurements of their properties are rare. With atom probe tomography, reliable analysis of singular features of the grain boundary structure becomes possible. We report microscopic measurements of segregation along individual TJ's in Fe/Cr. By segregation to TJ's nanometric tubular objects of distinct properties are formed. The determined segregation enthalpy of 0.076 eV indicates that TJ's provide considerable free volume similar to free surfaces.