High-temperature deformation mechanisms in a polycrystalline nickel-base superalloy studied by neutron diffraction and electron microscopy

To study the effect of gamma' precipitate size on the deformation behaviour of a polycrystalline nickel-based superalloy, model microstructures with a unimodal gamma' size distribution were developed and subjected to loading experiments at 750 degrees C. Neutron diffraction measurements were carried out during loading to record the elastic lattice strain response of the gamma and gamma' phase. A two-site elasto-plastic self-consistent model (EPSC) assisted in the interpretation of the elastic lattice strain response. In addition, the microstructures of the deformed specimens were analysed by (scanning) transmission electron microscopy (STEM). Excellent agreement was found between the EPSC and STEM results regarding a joint deformation of the gamma and gamma' phase in the fine gamma' microstructures and for low plastic strains in the medium gamma' microstructures. With increasing gamma' size and increasing degree of plastic deformation, both experimental methodologies revealed a tendency of the two phases to deform independently. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.