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617 results on '"Valiev, R.Z."'

104. The thermal behavior of atoms in ultrafine-grained Ni processed by severe plastic deformation

Author

Zhang, K., Alexandrov, I.V., Valiev, R.Z., and Lu, K.

Subjects
Nickel -- Research, Metals -- Thermal properties, Physics
Abstract

X-ray diffraction at various temperatures was conducted to investigate the features of the thermal behavior of atoms in ultrafine-grained (UFG) Ni processed by severe plastic deformation. An enhanced thermal expansion coefficient was observed in the UFG Ni sample, which was three times higher than in coarse-grained Ni polycrystal. The altered thermal properties in the UFG Ni sample were attributed to the nonequilibrium dislocations that disturb grain boundaries.

Published
1998

105. Structural characterization of nanocrystalline copper by means of x-ray diffraction

Author

Zhang, K., Alexandrov, I.V., Valiev, R.Z., and Lu, K.

Subjects
Copper -- Research, Crystals -- Research, Physics
Abstract

Quantitative x-ray diffraction measurements were conducted on a nanocrystalline Cu sample produced by severe plastic deformation. The shape of Bragg reflections were observed to be represented mainly by a Lorentzian function. A difference of as much as 6%+/-3% was found between the integrated intensities from the nanocrystalline and a reference coarse-grained Cu samples. Findings revealed that the grain sizes of nanocrystalline Cu in various crystallographic orientations are essentially the same, while the microstrains show substantial anisotropy.

Published
1996

149. Low-temperature superplasticity in nanostructured nickel and metal alloys

Author

McFadden, S.X., Mishra, R.S., Valiev, R.Z., Zhilyaev, A.P., and Mukherjee, A.K.

Subjects
Superplasticity -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Research into low-temperature superplasticity in nanocrystalline nickel, a nanocrystalline aluminium alloy and nanocrystalline nickel aluminide indicates that mechanistic details of superplasticity in nanocrystalline materials differ very significantly from those in microcrystalline materials. The most important observation in this research was the large reduction in superplastic temperatures. With nickel, a very low normalized temperature was achieved. It appears that it is not possible to obtain superplasticity in pure metals with a grain size of 100 nm or less, as the fall in superplastic temperature is balanced out by a reduction in the grain-growth temperature.

Published
1999

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