Characterisation of short fatigue cracks in titanium alloy IMI 834 using X-ray microtomography
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
A first attempt at the three-dimensional evaluation of naturally initiated surface connected and internal fatigue cracks is presented. Fatigue crack initiation and growth in air and vacuum environments have been investigated through X-ray microtomography in air and vacuum environments at elevated temperatures (350 °C), accompanied by post-mortem electron microscopy of the fracture surfaces. In vacuum (<10⁻⁵ mbar), multiple internal and surface-connected crack initiation was observed, but only the surface-connected cracks grew. In contrast, fewer cracks formed in air, these were mostly surface-connected and all were observed to grow. In all instances the initiation features were associated with globular primary α. An improved fatigue life was found in vacuum, which was mostly a consequence of delayed initiation, but was also due to slower fatigue crack propagation. The non-propagation of internal cracks was taken to imply that even the good laboratory vacuum obtained here was insufficient to simulate the conditions obtained for an internal crack in a component. The crack shape evolved towards a semi-circular shape a/c=1 in air during fatigue crack growth, whilst the vacuum cracks remained semi-elliptical (a/c≃1.4). This was taken to imply that oxide-induced crack closure played a role in fatigue crack growth in air.
Date Issued
2015-10-15
Date Acceptance
2015-07-29
Citation
Acta Materialia, 2015, 99 (1), pp.49-62
ISSN
1359-6454
Publisher
Elsevier
Start Page
49
End Page
62
Journal / Book Title
Acta Materialia
Volume
99
Issue
1
Copyright Statement
© 2015, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://www.sciencedirect.com/science/article/pii/S1359645415005558
Grant Number
EP/K034332/1
EP/L001748/1
EP/H004882/1
Subjects
Titanium
Fatigue
Tomography
Vacuum
Publication Status
Published
Date Publish Online
2015-08-08