Nanostructured Ni-Co alloys with tailorable grain size and twin density

TitleNanostructured Ni-Co alloys with tailorable grain size and twin density
Publication TypeJournal Article
Year of Publication2005
AuthorsWu, BYC, Ferreira, PJ, Schuh, CA
JournalMetallurgical and Materials Transactions a-Physical Metallurgy and Materials Science
Pagination1927 - 1936
Date Published2005/07//

We present an experimental approach to systematically produce nanostructures with various grain sizes and twin densities in the Ni-Co binary system. Using electrodeposition with various applied current densities and organic additive contents in the deposition bath, we synthesize nanostructured fee and hcp solid solutions with a range of compositions. Due to the low stacking fault energy (SFE) of these alloys, growth twins are readily formed during deposition, and by adjusting the deposition conditions, a range of twin boundary deinsities is possible. The resulting nanostructured alloys cannot be described by a single characteristic length scale, but instead must be characterized in terms of (1) a true grain size pertaining to general high-angle grain boundaries and (2) an effective grain size that incorporates twin boundaries. Analysis of Hall-Petch strength scaling for these materials is complicated by their dual length scales, but the hardness trends found in Ni-80Co are found to be roughly in line with those seen in pure nanocrystalline nickel.