Triple line diffusion in nanocrystalline Fe/Cr and its impact on thermal stability

Stender P, Balogh Z, Schmitz G

Abstract

The thermal reaction of iron–chromium multilayers is analyzed by atom-probe tomography. Sampleswere prepared using ion-beam sputter deposition and cutting by focused ion beams. Isothermal andisochronal annealing sequences were carried out in a vacuum furnace. Effects of atomic transport areobserved at temperatures above 773 K. Segregation along line-shaped zones is noticed to very highconcentrations. These zones, with a diameter of 1.5 nm, are identified as triple lines of the grain structure.While these defects could not be resolved by TEM, the outstanding potential of a 3D analysis provided byAPT allowed their detailed investigation. Evaluating the dependence of the segregation amplitude on timeand temperature, the segregation enthalpy and diffusivity of the triple lines are quantified. Thesegregation enthalpy is determined to be 0.076 eV, which indicates the considerable excess volume atthe triple line.