Phase morphology, variants and crystallography of alloy microstructures in cold dwell fatigue
File(s)
Published version
Author(s)
Zhang, Z
F.P.E., Dunne
Type
Journal Article
Abstract
This paper examines microscale crystal slip accumulation, cold creep, and stress redistribution (load shedding) related to dwell fatigue in a range of α–β Ti alloy microstructures. The role of basal slip and prism slip is evaluated in load shedding in a rogue grain combination. The results enrich the Stroh dislocation pile up interpretation of dwell by accounting for the anisotropic rate dependence of differing slip systems together with morphology.
Microstructural morphology has been found to play an essential role in cold creep and load shedding in dwell fatigue. Basketweave structures with multiple α variants have been shown to give the lowest load shedding for which the mechanistic explanation is that the β lath structures provide multiple, small-scale α variants which inhibit creep and hence stress relaxation, thus producing more uniform, diffuse stress distributions across the microstructure through microscale kinematic confinement, imposed by multi (α)-to-single (β) BOR relations (i.e. multiple α variants sharing the same parent β grain). The critical consequence of this is that alloys typically having multi-variant basketweave structure (e.g. Ti-6246), remain free of dwell fatigue debit whereas those alloys associated with globular colony structures (e.g. Ti-6242) suffer significant dwell debit. This understanding is important in microstructural design of titanium alloys for resisting cold dwell fatigue.
Microstructural morphology has been found to play an essential role in cold creep and load shedding in dwell fatigue. Basketweave structures with multiple α variants have been shown to give the lowest load shedding for which the mechanistic explanation is that the β lath structures provide multiple, small-scale α variants which inhibit creep and hence stress relaxation, thus producing more uniform, diffuse stress distributions across the microstructure through microscale kinematic confinement, imposed by multi (α)-to-single (β) BOR relations (i.e. multiple α variants sharing the same parent β grain). The critical consequence of this is that alloys typically having multi-variant basketweave structure (e.g. Ti-6246), remain free of dwell fatigue debit whereas those alloys associated with globular colony structures (e.g. Ti-6242) suffer significant dwell debit. This understanding is important in microstructural design of titanium alloys for resisting cold dwell fatigue.
Date Issued
2018-08-01
Date Acceptance
2018-03-23
Citation
International Journal of Fatigue, 2018, 113, pp.324-334
ISSN
0142-1123
Publisher
Elsevier
Start Page
324
End Page
334
Journal / Book Title
International Journal of Fatigue
Volume
113
Copyright Statement
© 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/)
Subjects
Science & Technology
Technology
Engineering, Mechanical
Materials Science, Multidisciplinary
Engineering
Materials Science
Cold dwell fatigue
Titanium alloy
Creep
Basketweave
Variants
Microscale kinematic confinement
Burgers orientation relationship
ALPHA/BETA-TITANIUM-ALLOY
ROOM-TEMPERATURE DEFORMATION
STRAIN-RATE SENSITIVITY
CRYSTAL PLASTICITY FE
CRACK-GROWTH
TEXTURE HETEROGENEITIES
MECHANICAL-PROPERTIES
TI ALLOYS
NUCLEATION
TI-6AL-4V
0913 Mechanical Engineering
0905 Civil Engineering
Mechanical Engineering & Transports
Publication Status
Published
Date Publish Online
2018-03-26