Investigation of slip transfer across HCP grain boundaries with application to cold dwell facet fatigue
File(s)
Published version
Author(s)
Zheng, Z
Balint, D
Dunne, F
Type
Journal Article
Abstract
This paper addresses the role of grain boundary slip transfer and thermally-activated discrete
dislocation plasticity in the redistribution of grain boundary stresses during cold dwell fatigue in
titanium alloys. Atomistic simulations have been utilised to calculate the grain boundary energies for
titanium with respect to the misorientation angles. The grain boundary energies are utilised within a
thermally-activated discrete dislocation plasticity model incorporating slip transfer controlled by
energetic and grain boundary geometrical criteria. The model predicts the grain size effect on the flow
strength in Ti alloys. Cold dwell fatigue behaviour in Ti-6242 alloy is investigated and it is shown that
significant stress redistribution from soft to hard grains occurs during the stress dwell, which is
observed both for grain boundaries for which slip transfer is permitted and inhibited. However, the
grain boundary slip penetration is shown to lead to significantly higher hard-grain basal stresses near
the grain boundary after dwell, thus exacerbating the load shedding stress compared to an
impenetrable grain boundary. The key property controlling the dwell fatigue response is argued to
remain the time constant associated with the thermal activation process for dislocation escape, but the
slip penetrability is also important and exacerbates the load shedding. The inclusion of a macrozone
does not significantly change the conclusions but does potentially lead to the possibility of a larger
initial facet.
dislocation plasticity in the redistribution of grain boundary stresses during cold dwell fatigue in
titanium alloys. Atomistic simulations have been utilised to calculate the grain boundary energies for
titanium with respect to the misorientation angles. The grain boundary energies are utilised within a
thermally-activated discrete dislocation plasticity model incorporating slip transfer controlled by
energetic and grain boundary geometrical criteria. The model predicts the grain size effect on the flow
strength in Ti alloys. Cold dwell fatigue behaviour in Ti-6242 alloy is investigated and it is shown that
significant stress redistribution from soft to hard grains occurs during the stress dwell, which is
observed both for grain boundaries for which slip transfer is permitted and inhibited. However, the
grain boundary slip penetration is shown to lead to significantly higher hard-grain basal stresses near
the grain boundary after dwell, thus exacerbating the load shedding stress compared to an
impenetrable grain boundary. The key property controlling the dwell fatigue response is argued to
remain the time constant associated with the thermal activation process for dislocation escape, but the
slip penetrability is also important and exacerbates the load shedding. The inclusion of a macrozone
does not significantly change the conclusions but does potentially lead to the possibility of a larger
initial facet.
Date Issued
2017-01-11
Date Acceptance
2017-01-09
Citation
Acta Materialia, 2017, 127, pp.43-53
ISSN
1359-6454
Publisher
Elsevier
Start Page
43
End Page
53
Journal / Book Title
Acta Materialia
Volume
127
Copyright Statement
© 2017 Acta Materialia Inc. Published by Elsevier Ltd. This is an open access article under the CC BY
license (http://creativecommons.org/licenses/by/4.0/).
license (http://creativecommons.org/licenses/by/4.0/).
Sponsor
Engineering & Physical Science Research Council (EPSRC)
EPSRC
Grant Number
EP/K034332/1
EP/K034332/1
Subjects
Materials
0912 Materials Engineering
0913 Mechanical Engineering
Publication Status
Published