1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Pr. Nauky, Kharkiv 61103, Ukraine
2Institute of Low Temperature and Structure Researches, Polish Academy of Science, 2 ul. Okólna, Wrocław, 50-422, Poland
3O.O. Galkin Donetsk Institute for Physics and Engineering NAS of Ukraine, Kyiv 03680, Ukraine
4G.V. Kurdyumov Institute for Metal Physics National of the Sciences of Ukraine 36 Academician Vernadsky Blvd., UA-03680, Kiev-142, Ukraine
Received April 22, 2016
The main microstructure features of UFG Cu–OF polycrystals processed by direct and equal-channel angular hydroextrusion were studied by EBSD and XRD methods. The effect of microstructure on the temperature dependencies of yield stress and strain rate stress sensitivity of polycrystals was investigated at tension and stress relaxation tests in the insufficiently explored temperature range of 4.2–300 K. From the thermally activated analysis the forest intersection mechanism was determined as rate controlling of plastic deformation in the range 77–200 K and its empirical parameters were obtained. The experimental anomalies below 77 K as deviations from thermally activated intersection process were explained by inertial dislocation properties revealed at high effective stress and low dynamic friction of dislocations. The inverse temperature dependencies of activation volume revealed above 200 K were attributed to the thermally activated grain boundary dislocation depining relevant for UFG structure.
PACS: 61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.); PACS: 62.20.F– Deformation and plasticity; PACS: 62.20.–x Mechanical properties of solids; PACS: 81.40.Lm Deformation, plasticity, and creep.