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Title: Low cycle fatigue of a directionally solidified nickel-based superalloy: testing, characterisation and modelling
Authors: Kashinga, Rudolph J.
Zhao, Liguo
Silberschmidt, Vadim V.
Farukh, Farukh
Barnard, N.C.
Whittaker, M.T.
Proprentner, Daniela
Shollock, Barbara
McColvin, G.
Keywords: Low cycle fatigue
Directional solidification
Crystal plasticity
Grain misorientations
Stress concentration
Issue Date: 2017
Publisher: Elsevier (© The Authors)
Citation: KASHINGA, R.J. ... et al, 2017. Low cycle fatigue of a directionally solidified nickel-based superalloy: testing, characterisation and modelling. Materials Science and Engineering: A, 708, (December 2017), pp. 503-513.
Abstract: Low cycle fatigue (LCF) of a low-carbon (LC) directionally-solidified (DS) nickel-base superalloy, CM247 LC DS, was investigated using both experimental and computational methods. Strain-controlled LCF tests were conducted at 850°C, with a loading direction either parallel or perpendicular to the solidification direction. Trapezoidal loading-waveforms with 2 s and 200 s dwell times imposed at the minimum and the maximum strains were adopted for the testing. A constant strain range of 2% was maintained throughout the fully-reversed loading conditions (strain ratio R = −1). The observed fatigue life was shorter when the loading direction was perpendicular to the solidification one, indicating an anisotropic material response. It was found that the stress amplitude remained almost constant until final fracture, suggesting limited cyclic hardening/softening. Also, stress relaxation was clearly observed during the dwell period. Scanning Electron Microscopy fractographic analyses showed evidence of similar failure modes in all the specimens. To understand deformation at grain level, crystal plasticity finite element modelling was carried out based on grain textures measured with EBSD. The model simulated the full history of cyclic stress-strain responses. It was particularly revealed that the misorientations between columnar grains resulted in heterogeneous deformation and localised stress concentrations, which became more severe when the loading direction was normal to a solidification direction, explaining the shorter fatigue life observed.
Description: This is an Open Access Article. It is published by Elsevier under the Creative Commons Attribution 4.0 International Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/4.0/
Sponsor: The work was funded by the EPSRC (Grants EP/K026844/1 and EP/M000966/1) of the UK, and in collaboration with GE Power, Dstl and Uniper.
Version: Published
DOI: 10.1016/j.msea.2017.10.024
URI: https://dspace.lboro.ac.uk/2134/26921
Publisher Link: https://doi.org/10.1016/j.msea.2017.10.024
ISSN: 0921-5093
Appears in Collections:Published Articles (Mechanical, Electrical and Manufacturing Engineering)

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