TY - JOUR A1 - Epishin, A. A1 - Link, T. A1 - Svetlov, I. L. A1 - Nolze, Gert A1 - Saliwan Neumann, Romeo A1 - Lucas, H. T1 - Mechanism of porosity growth during homogenisation in single crystal nickel-based superalloys N2 - Several mechanisms for porosity growth in single crystal nickel-based superalloys during homogenisation heat treatment have been proposed in the literature. They were carefully checked using different experimental methods, namely quantitative light microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and density measurements. It is shown that the main mechanism is the Kirkendall–Frenkel effect, i.e. generation of voids due to uncompensated efflux of Al atoms from dissolving γ/γ′-eutectic areas. The Al diffusion is supported by the afflux of vacancies from surrounding γ-matrix which results in porosity growth. This conclusion is confirmed by the estimation of the vacancy afflux towards the dissolving eutectic. KW - Ni-base superalloy KW - Eutectic KW - Vacancies KW - Porosity PY - 2013 VL - 104 IS - 8 SP - 776 EP - 782 PB - Carl Hanser Verlag AN - OPUS4-37983 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Epishin, A. I. A1 - Link, T. A1 - Nolze, Gert A1 - Svetlov, I. L. A1 - Bokshtein, B. S. A1 - Rodin, A. O. A1 - Saliwan Neumann, Romeo A1 - Oder, Gabriele T1 - Diffusion processes in multicomponent nickel-base superalloy-nickel system N2 - Optical and scanning electron microscopy, as well as electron microprobe analysis and electron backscatter diffraction, have been used to study diffusion processes that occur in a diffusion pair that consistsof a single-crystal CMSX-10 nickel-base superalloy and polycrystalline nickel, at temperatures of 1050–1250°C. It has been found that, in this system, the distributions of γ-stabilizing elements (Cr, Co, W, and Re) are described by the Boltzmann solution for diffusion between two semiinfinite plates of a binary alloy. The processing of these distributions has shown that the diffusion coefficients of Cr, Co, W, and Re in the multicomponent system are close to those in binary alloys of these elements with Ni. The diffusion redistribution of the elements leads to the dissolution of the γ′ phase in the nickel-base superalloy, growth of nickel grains toward the superalloy constituent of the diffusion pair, and the formation of porosity on both sides of the migrating interface, which is determined from a crystal misorientation of the alloy single crystal and nickel grains. KW - Ni-base superalloy KW - Interface KW - Diffusion KW - Phase transformation KW - Porosity PY - 2014 SN - 0031-918X VL - 115 IS - 1 SP - 21 EP - 29 AN - OPUS4-37980 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -