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

Triple Line Diffusion in Nanocrystalline Fe/Cr and its Impact on Thermal Stability. P.Stender, Z.Balogh, G.Schmitz: Ultramicroscopy, 2011, 111[6], 524-9