Thermal Stability of Nanocrystalline Ni
A.V. Korznikova, Z. Pakiełab and K.J. Kurzydłowskib
aInstitute of Problems of Metal Superplasticity, Russian Academy of Sciences, Khalturina 39, Ufa, 450001 Bashkortostan, Russia
bFaculty of Materials Science and Engineering, Warsaw University of Technology, Wołoska 141, 02-507 Warsaw, Poland
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Ultrafine-grained structure with grain size of about 100 nm was obtained in nickel by deformation under a pressure of 7 GPa in Bridgman anvils. The structure evolution in ultrafine-grained nickel was studied by residual resistance, transmission electron microscopy, X-ray diffraction, and microhardness measurements. It was established that the evolution of the structure upon heating of ultrafine-grained nickel may be divided into three stages. Stage A corresponds to temperatures below 453 K and is characterised by an insignificant decrease in the resistivity and microhardness. At this stage, a decrease in the internal stresses is not accompanied by grain growth. Stage B, corresponding to the temperatures range of 453--513 K, is characterised by an abrupt decrease in the resistivity and hardness, disappearance of the internal stresses, and by an intense grain growth. Stage C (above 523 K) corresponds to an insignificant increase in the resistivity and further decrease in the hardness.
DOI: 10.12693/APhysPolA.102.265
PACS numbers: 62.25.+g, 73.63.Bd