Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 527, Issue 4-5, Pages 1206-1214Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2009.09.050
Keywords
Nickel; Powder metallurgy; Multi-modal microstructure; Mechanical properties
Categories
Funding
- National Research Agency [ANR 09-BLAN-0010-01]
- Agence Nationale de la Recherche (ANR) [ANR-09-BLAN-0010] Funding Source: Agence Nationale de la Recherche (ANR)
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Near fully dense polycrystalline nickel with a random crystallographic texture was consolidated by hot isostatic pressing of blends of nanocrystalline and conventional microcrystalline powders with different volume fractions. The transformation process resulted in a composite-like microstructure constituted by clusters of soft coarse grains regularly distributed in a hard ultrafine-grained matrix. It was found that the ultrafine-grained matrix hinders the coalescence of the coarse grains component during sintering resulting in a smaller grain size than in the fully coarse-grained counterpart in a sort of barrier effect. This effect was found to depend on the volume fraction of the ultrafine-grained matrix. Conversely, during the hot isostatic pressing, the plastic deformation of the coarse-grained fraction is preferred to that of the ultrafine-grained fraction, because of greater dislocation activity in the former type of grains, resulting in lower defect densities in the ultrafine-grained matrix (shielding effect). It is shown that as a result of the interplay between the coarse-grained and ultrafine-grained components during sintering, the mechanical behavior of the composite materials cannot be obtained by a linear interpolation between the characteristics of fully ultrafine-grained and coarse-grained counterparts. (C) 2009 Elsevier B.V. All rights reserved.
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