A new class of bulk nanocrystalline nickel dispersed with nano-scale WO 3 particles has been synthesized by conventional electrodeposition to clarify the effect of the presence of nano-size dispersions on the strength and thermal stability of nanocrystalline structures. It was found that WO 3 particles of an initial size of 0.1 lm, when suspended in an electrolyte, fragmented into smaller nano-size particles, and were embedded into nanocrystalline nickel matrix of an average grain size of 45 nm during deposition. X-ray diffraction and transmission electron microscopy analyses revealed that phase transition of WO 3 particles occurred from an initial monoclinic to a tetragonal structure. The cause-and-effect relation between the fragmentation and the phase transition of WO 3 particles was discussed. Further hardening was confirmed in comparison with nanocrystalline pure nickel, but its increment was less than that predicted by the classical Orowan-type hardening of the particle-dislocation interaction. The discrepancy may be associated with a different dominant deformation mode which operates in a nanocrystalline regime.

A new class of bulk nanocrystalline nickel dispersed with nano-scale WO 3 particles has been synthesized by conventional electrodeposition. It was found that WO 3 particles of an initial size of 0.1 µm, when suspended in an electrolyte, fragmented into smaller nano-scale particles during deposition accompanied by phase transition from an initial monoclinic to tetragonal structure. The cause and effect relation between the fragmentation and the phase transition of WO 3 particles was discussed. Hopefully, the phenomenon can be applied to establish a novel synthesis for a new class of bulk nanocrystalline metals with dispersed nano-scale particles endowed with higher strength and thermal stability than conventional mono-phase nanocrystalline materials.

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