skip to main content

Title: Investigation of deformation micro-mechanisms in nickel consolidated from a bimodal powder by spark plasma sintering

Bulk polycrystalline nickel compact was processed by spark plasma sintering from heterogeneous powder consisting of a mixture of nanometer and micrometer sized particles. The consolidated samples inherited the bimodal structure of the starting powder and was composed of ~ 55 vol.% coarse-grained (with the grain size larger than 1 μm) and ~ 45 vol.% ultrafine-grained (with an average grain size of ~ 550 nm) components. The deformation mechanisms were established by EBSD, X-ray line profile analysis and in-situ TEM observations. In the ultrafine-grained volume, the deformation occurred mainly through the activation of dislocation sources emitting full or partial dislocation either from grain interior or grain boundaries. Besides dislocation activity, rolling and sliding of nanograins were also observed during deformation by in-situ transmission electron microscopy, which have a considerable contribution to the observed high strain rate sensitivity of the bimodal microstructure. The cracks formed during deformation easily propagated in the nanograin regions due to the weaker particle bonding caused by the relatively high fraction of native oxide layer on the surface of the initial nanoparticles. - Highlights: • Bulk bimodal polycrystalline Ni was processed by SPS from a heterogeneous powder. • High SRS of the flow stress was observed which enhancedmore » ductility and strength. • In-situ TEM revealed dislocation sources inside and at the boundaries of UFGs. • Twinning, partial dislocation and NG rolling were observed at crack tip vicinity. • The high SRS pertained to both dislocation activity in CG and NG rolling.« less
Authors:
 [1] ;  [2] ; ;  [3] ;  [2] ;  [1]
  1. Université Paris 13, Sorbonne Paris Cité, LSPM, CNRS, 99 Avenue J.B. Clément, 93430 Villetaneuse (France)
  2. Department of Materials Physics, Eötvös Loránd University Budapest, P.O.B. 32, H-1518 (Hungary)
  3. Université de Toulouse and CEMES, CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France)
Publication Date:
OSTI Identifier:
22476011
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 99; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BACKSCATTERING; CRACKS; DEFORMATION; DISLOCATIONS; DUCTILITY; ELECTRON DIFFRACTION; FLOW STRESS; GRAIN BOUNDARIES; GRAIN SIZE; LAYERS; NANOSTRUCTURES; NICKEL; POLYCRYSTALS; POWDERS; SENSITIVITY; SINTERING; STRAIN RATE; SURFACES; TRANSMISSION ELECTRON MICROSCOPY