s41598-017-10091-w.pdf (2.54 MB)
Download file

The contrasting roles of creep and stress relaxation in the time-dependent deformation during in-situ cooling of a nickel-base single crystal superalloy.

Download (2.54 MB)
journal contribution
posted on 30.04.2020, 14:11 by Chinnapat Panwisawas, Neil D'Souza, David M Collins, Ayan Bhowmik
Time dependent plastic deformation in a single crystal nickel-base superalloy during cooling from casting relevant temperatures has been studied using a combination of in-situ neutron diffraction, transmission electron microscopy and modelling. Visco-plastic deformation during cooling was found to be dependent on the stress and constraints imposed to component contraction during cooling, which mechanistically comprises creep and stress relaxation. Creep results in progressive work hardening with dislocations shearing the γ' precipitates, a high dislocation density in the γ channels and near the γ/γ' interface and precipitate shearing. When macroscopic contraction is restricted, relaxation dominates. This leads to work softening from a decreased dislocation density and the presence of long segment stacking faults in γ phase. Changes in lattice strains occur to a similar magnitude in both the γ and γ' phases during stress relaxation, while in creep there is no clear monotonic trend in lattice strain in the γ phase, but only a marginal increase in the γ' precipitates. Using a visco-plastic law derived from in-situ experiments, the experimentally measured and calculated stresses during cooling show a good agreement when creep predominates. However, when stress relaxation dominates accounting for the decrease in dislocation density during cooling is essential.

History

Citation

Scientific Reports, 2017, 7, 11145

Author affiliation

School of Engineering

Version

VoR (Version of Record)

Published in

Scientific Reports

Volume

7

Issue

1

Pagination

11145

Publisher

Nature Research

eissn

2045-2322

Acceptance date

03/08/2017

Copyright date

2017

Publisher version

https://www.nature.com/articles/s41598-017-10091-w#Abs1

Language

eng

Usage metrics

Categories

Licence

Exports