RESUMO
Two Ti alloys with compositions Ti-10Ta and Ti-10Nb (at.%) were milled in a high-energy mill for a maximum of 80 h in an argon atmosphere. A nanocrystalline structure of alpha-Ti(X) (X = Ta or Nb) solid solution was formed in both investigated alloys after milling, as shown by X-ray diffraction. Transmission electron microscopy observations of powders milled for 80 h revealed chemical inhomogeneity of particles in nanometre-scale regions and an average crystallite size of about 10 nm. The pulse plasma sintering method was applied for hot consolidation of milled powders. The mean density of pulse plasma sintering compacts of Ti-Nb alloy was about 99.5% of the theoretical value, whereas the density of the Ti-10Ta sample was lower, close to 92% of the theoretical value. Transmission electron microscopy observation of compacted samples showed that the sintering process caused the formation of a two-phase alpha + beta structure in both investigated alloys, with a mean grain size of 220 nm. The chemical inhomogeneity and high degree of deformation in nanometre-scale regions of milled powders led to a martensitic transformation, resulting in formation of a 9R martensite structure.
RESUMO
ZrNiTiCu and ZrNiTiCuAl alloys were amorphized using either a melt-spinning or ball-milling process in a high-energy planetary mill. The elemental powders were initially blended to the desired composition (in at.%) of Zr, 65; Cu, 27.5; Al, 7.5 and of Ti, 25; Zr, 17; Cu, 29; Ni, 29, respectively. The composition of alloys was chosen to be the same as for the bulk amorphous ZrCuAl and easy glass-forming ZrNiTiCu alloys. An almost fully amorphous structure was obtained after 80 h of milling in the case of both compositions. Transmission electron microscopy studies of ball-milled powders revealed the presence of nano-crystallites [2-5 nm for ZrCuAl and smaller (1-3 nm) for the ZrTiNiCu alloy]. High-resolution transmission electron microscopy of melt-spun ZrNiTiCuAl ribbons provided evidence of the amorphous structure.