Fizika Nizkikh Temperatur: Volume 43, Number 12 (December 2017), p. 1780-1788    ( to contents , go back )

Unstable plastic deformation of ultrafine-grained copper at temperature of 0.5 K

N.V. Isaev1, T.V. Grigorova1, S.E. Shumilin1, S.S. Polishchuk2, and O.A. Davydenko3

1B. Verkin Institute for Low Temperature Physics and Engineering, NASU, Kharkov 61103, Ukraine
E-mail: isaev@ilt.kharkov.ua

2G.V. Kurdyumov Institute for Metal Physics, NASU, 36 Acad. Vernadsky Boulevard, Kyiv 03680, Ukraine

3О.О. Galkin Donetsk Institute of Physics and Engineering, 46 Nauki Ave., Kyiv 03680, Ukraine

Received May 14, 2017

Abstract

It was studied the relation between the strain hardening rate and the flow stress instability in Cu–OF polycrystals deformed by tension at constant strain rate in the liquid 3He atmosphere. Microstructures of the samples after equal-channel angular hydro-extrusion processing and after annealing at recovery or recrystallization temperatures were controlled by x-ray diffraction. It is shown that the unstable plastic deformation revealed as macroscopic stress jumps (busts) on the tension curves appears at some threshold stress assumed sufficient for activate a dynamic recovery which give rise to decrease the coefficient of strain hardening. The effect of grain size and initial dislocation density on the scale and statistics of the low temperature unstable flow is discussed.

PACS: 62.20.F– Deformation and plasticity;
PACS: 62.20.–x Mechanical properties of solids.

Key words: work hardening, unstable flow, low tem-perature, copper policrystals.

Published online: October 25, 2017

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