Microstructure and strength of nanocrystalline copper alloy prepared by mechanical alloying

The origins of strengthening in nanostructured metals and alloys

“…Since particles tend to pin grain boundaries, grain size and particle size are often related, for example by the Zener relation, d = 0.66 f/√f, grain size and particle separation may be related: (14) Orowan strengthening models can clearly only be used for materials with a small volume fraction of second phase, say less than 10 %, but are independent of grain size. Figure 5 shows an analysis of strengthening in copper alloys containing second phase particles [65] , where strength is related to the Orowan mechanism. A good description of the particle strengthening, i.e.…”

“…When the grain size is very small, these fine particles have sizes similar to the grain size, and it may be better to consider the material as a composite mixture of matrix grains and particles. Orowan hardening by fine particles, size s, present in volume fraction f in a material of grain size d >> f, can be described as: (13) where m is the Taylor factor, G the shear modulus, b the Burgers vector and l the separation of particles on the shear plane [65] . Since particles tend to pin grain boundaries, grain size and particle size are often related, for example by the Zener relation, d = 0.66 f/√f, grain size and particle separation may be related: (14) Orowan strengthening models can clearly only be used for materials with a small volume fraction of second phase, say less than 10 %, but are independent of grain size.…”

“…These Figure 5. analysis of strengthening in Cu-bcc particle materials in terms of the orowan strengthening model, from morris and morris [65] . [65] .…”

Microstructure-strength relationship of a deformation processed aluminum-titanium composite

“…The exceptionally large interfacial boundary area present in such plane-straining microstructures (as seen in Cu-X and Ti-Y) might also explain the anomalous strengthening observed in FCCBCC Cu-X composites but absent in FCCLFCC composites such as Ag-Cu [32]. The increase in strength observed for the Ti-20Y composite in Figure 6 is quite similar to that observed in the Cu-20Nb composites over the range 0 I q I 7.27 [l, 41. As previously mentioned, the Ti-20Y composites did not maintain the desired foldedribbon microstructure at strains greater than r\ = 7.27.…”

Electrodeposited Nanocrystalline Nickel Dispersed with Nano-Size WO₃ Particles

“…13) For example, additive strengthening by Orowan-type dislocationparticle interaction and the HallPetch effect in nanocrystalline materials has been discussed. 1) In addition to their strengthening, such very fine particles can stabilize the nanocrystalline structure whose low thermal stability is a drawback of nanocrystalline materials and has limited their industrial application in spite of very high interest in the scientific community. 4) Particle dispersions or precipitates to pin grain boundaries are common kinetic approaches to stabilize the structures.…”