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Materials 2017, 10(1), 61;

Creep Deformation by Dislocation Movement in Waspaloy

Institute of Materials, Bay Campus, Swansea University, Swansea SA1 8EN, UK
Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS, UK
Rolls-Royce plc, Elton Road, Derby DE24 8BJ, UK
Author to whom correspondence should be addressed.
Academic Editor: Richard Thackray
Received: 25 October 2016 / Revised: 5 January 2017 / Accepted: 5 January 2017 / Published: 12 January 2017
(This article belongs to the Special Issue The Life of Materials at High Temperatures)
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Creep tests of the polycrystalline nickel alloy Waspaloy have been conducted at Swansea University, for varying stress conditions at 700 °C. Investigation through use of Transmission Electron Microscopy at Cambridge University has examined the dislocation networks formed under these conditions, with particular attention paid to comparing tests performed above and below the yield stress. This paper highlights how the dislocation structures vary throughout creep and proposes a dislocation mechanism theory for creep in Waspaloy. Activation energies are calculated through approaches developed in the use of the recently formulated Wilshire Equations, and are found to differ above and below the yield stress. Low activation energies are found to be related to dislocation interaction with γ′ precipitates below the yield stress. However, significantly increased dislocation densities at stresses above yield cause an increase in the activation energy values as forest hardening becomes the primary mechanism controlling dislocation movement. It is proposed that the activation energy change is related to the stress increment provided by work hardening, as can be observed from Ti, Ni and steel results. View Full-Text
Keywords: creep; dislocations; Wilshire equations; forest hardening creep; dislocations; Wilshire equations; forest hardening

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Whittaker, M.; Harrison, W.; Deen, C.; Rae, C.; Williams, S. Creep Deformation by Dislocation Movement in Waspaloy. Materials 2017, 10, 61.

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