Evolution of a Nanocrystalline Structure of the Cobalt Metal in Annealing

Authors L.A. Gabdrakhmanova1 , K.M. Mukashev2 , F.F. Umarov3 , A.D. Muradov2 , G.Sh. Yar-Mukhamedova2

1Bashkir State University, Ufa, Bashkortostan, Russia

2Al-Farabi Kazakh National University, Almaty, Kazakhstan

3Kazakh-British Technical University, Almaty, Kazakhstan

Е-mail mukashev.kms@gmail.com
Issue Volume 12, Year 2020, Number 6
Dates Received 29 July 2020; revised manuscript received 20 December 2020; published online 25 December 2020
Citation L.A. Gabdrakhmanova, K.M. Mukashev, F.F. Umarov, et al., J. Nano- Electron. Phys. 12 No 6, 06027 (2020)
DOI https://doi.org/10.21272/jnep.12(6).06027
PACS Number(s) 61.46.Df, 71.20.Gj
Keywords Nanocrystals (3) , Diffusion (11) , Grain growth, Defects (12) , Dislocations (2) , Recrystallization, Activation energy (7) .

It is shown that the boundaries of grains formed during severe plastic deformation of cobalt are high-angle, nonequilibrium, adjacent to distorted regions of the crystal lattice. These distortions are caused by the fields of elastic stresses introduced by grain boundary dislocations. The density of dislocations in the bulk of nanocrystals reaches 1010 cm2. The large length of nonequilibrium boundaries and the high density of defects play a decisive role in the formation of physical and mechanical properties and determine the low thermal stability of nanocrystalline materials: grain growth begins at relatively low temperatures during the recovery of the cobalt structure. This process develops smoothly up to 300 (С. A sharp change in these properties occurs during recrystallization at T > 300 (C and then they practically do not change. Above T > 400 (C, the cobalt structure became completely recrystallized and further coarsening of grains is observed. In this case, the abnormal growth of perfect grains occurs due to the absorption of small imperfect cells. As a result of the redistribution and annihilation of dislocations in the boundaries and in the volume of grains, the processes of recrystallization occur according to the diffusion mechanism.

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