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Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations

J.Y. Guédou, C. Deen, M.T. Whittaker, W. Harrison, C.M.F. Rae, S.J. Williams, J. Choné, Mark Whittaker Orcid Logo

MATEC Web of Conferences, Volume: 14, Start page: 15001

Swansea University Author: Mark Whittaker Orcid Logo

DOI (Published version): 10.1051/matecconf/20141415001

Abstract

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, nota...

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Published in: MATEC Web of Conferences
Published: 2014
URI: https://cronfa.swan.ac.uk/Record/cronfa21251
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spelling 2016-04-18T13:58:37.9368811 v2 21251 2015-05-08 Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations a146c6d442cb2c466d096179f9ac97ca 0000-0002-5854-0726 Mark Whittaker Mark Whittaker true false 2015-05-08 MTLS 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, notably those with stresses 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. In particular, the roles of recovery, tertiary gamma prime particles and dislocation foresting are examined, and related back to observations from the Wilshire fits. The virgin (untested) material has been forged and heat treated, containing some recrystallised material together with areas of more heavily deformed and recovered material clustered around the grain boundaries. Observations from tests below the 0.2% proof stress show relatively low dislocation densities away from grain boundaries and dislocation movement can be seen to be governed by interactions with the γ′ precipitates. In contrast, above the 0.2% proof stress, TEM observations show a substantially greater density of dislocations. The increased density provides an increment of strength through forest hardening. At stresses above the original yield point, determined by the precipitates, the creep rate is controlled by inter-action with the dislocation forest and results in an apparent activation energy change. 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. Journal Article MATEC Web of Conferences 14 15001 31 12 2014 2014-12-31 10.1051/matecconf/20141415001 COLLEGE NANME Materials Science and Engineering COLLEGE CODE MTLS Swansea University 2016-04-18T13:58:37.9368811 2015-05-08T13:43:40.9032255 College of Engineering Engineering J.Y. Guédou 1 C. Deen 2 M.T. Whittaker 3 W. Harrison 4 C.M.F. Rae 5 S.J. Williams 6 J. Choné 7 Mark Whittaker 0000-0002-5854-0726 8 0021251-17032016130440.pdf Cronfav3.pdf 2016-03-17T13:04:40.3200000 Output 2175583 application/pdf Version of Record true 2016-03-17T00:00:00.0000000 true
title Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations
spellingShingle Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations
Mark Whittaker
title_short Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations
title_full Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations
title_fullStr Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations
title_full_unstemmed Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations
title_sort Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations
author_id_str_mv a146c6d442cb2c466d096179f9ac97ca
author_id_fullname_str_mv a146c6d442cb2c466d096179f9ac97ca_***_Mark Whittaker
author Mark Whittaker
author2 J.Y. Guédou
C. Deen
M.T. Whittaker
W. Harrison
C.M.F. Rae
S.J. Williams
J. Choné
Mark Whittaker
format Journal article
container_title MATEC Web of Conferences
container_volume 14
container_start_page 15001
publishDate 2014
institution Swansea University
doi_str_mv 10.1051/matecconf/20141415001
college_str College of Engineering
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hierarchy_top_title College of Engineering
hierarchy_parent_id collegeofengineering
hierarchy_parent_title College of Engineering
department_str Engineering{{{_:::_}}}College of Engineering{{{_:::_}}}Engineering
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description 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, notably those with stresses 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. In particular, the roles of recovery, tertiary gamma prime particles and dislocation foresting are examined, and related back to observations from the Wilshire fits. The virgin (untested) material has been forged and heat treated, containing some recrystallised material together with areas of more heavily deformed and recovered material clustered around the grain boundaries. Observations from tests below the 0.2% proof stress show relatively low dislocation densities away from grain boundaries and dislocation movement can be seen to be governed by interactions with the γ′ precipitates. In contrast, above the 0.2% proof stress, TEM observations show a substantially greater density of dislocations. The increased density provides an increment of strength through forest hardening. At stresses above the original yield point, determined by the precipitates, the creep rate is controlled by inter-action with the dislocation forest and results in an apparent activation energy change. 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.
published_date 2014-12-31T03:30:51Z
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