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Point Defects and High-Temperature Deformation of NiO

Published online by Cambridge University Press:  28 February 2011

K. C. Goretta
Affiliation:
Work performed under a laboratory graduate participantship at Argonne National Laboratory. Program administered by the Argonne Division of Education Programs with funding from the U.S. Department of Energy.
J. L. Routbort
Affiliation:
Materials Science and Technology Division, Argonne National Laboratory, Argonne, IL 60439
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Abstract

The steady-state flow stress τs in nonstoichiometric NiO single crystals has been measured in the temperature range of 1428 to 1653 K with oxygen partial pressures p(O2) between 6 and 1×105 Pa. Strain rates were varied from 1×10−5 to 2×10−3 s−1. Transmission electron microscopy indicates that dislocation climb is the primary mechanism of recovery. Because dislocation climb is diffusion controlled, the data may be described at fixed temperature by = Aτns (O2)1/m, where n is the stress exponent and m is a parameter that is determined by the dominant atomic defects on each sublattice. At high temperatures and p(O2) > 2×104 Pa, n was found to be in agreement with dislocation-climb models; however, n increased at low p(O2) owing to effects of impurities. The values of m are consistent with control of climb rate by diffusion of singly charged oxygen vacancies for low p(O2) and by diffusion of neutral oxygen interstitials for high p(O2). At lower temperatures, the values of n are strongly affected by dislocation/impurity interactions for all p(O2).

Type
Research Article
Copyright
Copyright © Materials Research Society 1986

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