Using transmission Kikuchi diffraction to characterise α variants in an α+β titanium alloy
File(s)TONG_et_al-2017-Journal_of_Microscopy.pdf (2.71 MB)
Published version
Author(s)
Tong, VS
Joseph, S
Ackerman, A
Dye
Britton
Type
Journal Article
Abstract
Two phase titanium alloys are important for high-performance engineering components, such as aeroengine discs. The microstructures of these alloys are tailored during thermomechanical processing to precisely control phase fractions, morphology and crystallographic orientations. In bimodal two phase (α + β) Ti-6Al-2Sn-4Zr-2Mo (Ti-6242) alloys there are often three microstructural lengthscales to consider: large (∼10 μm) equiaxed primary α; >200 nm thick plate α with a basketweave morphology; and very fine scaled (<50 nm plate thickness) secondary α that grows between the larger α plates surrounded by retained β. In this work, we utilise high spatial resolution transmission Kikuchi diffraction (TKD, also known as transmission-based electron backscatter diffraction, t-EBSD) and scanning electron microscopy (SEM)-based forward scattering electron imaging to resolve the structures and orientations of basketweave and secondary α in Ti-6242. We analyse the α variants formed within one prior β grain, and test whether existing theories of habit planes of the phase transformation are upheld. Our analysis is important in understanding both the thermomechanical processing strategy of new bimodal two-phase titanium alloys, as well as the ultimate performance of these alloys in complex loading regimes such as dwell fatigue. Our paper champions the significant increase in spatial resolution afforded using transmission techniques, combined with the ease of SEM-based analysis using conventional electron backscatter diffraction (EBSD) systems and forescatter detector (FSD) imaging, to study the nanostructure of real-world engineering alloys.
Date Issued
2017-05-04
Date Acceptance
2017-03-25
Citation
Journal of Microscopy, 2017, 267 (3), pp.318-329
ISSN
1365-2818
Publisher
Wiley
Start Page
318
End Page
329
Journal / Book Title
Journal of Microscopy
Volume
267
Issue
3
Copyright Statement
© 2017 The Authors. Journal of Microscopy published by JohnWiley & Sons Ltd on behalf of Royal Microscopical Society.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Sponsor
Engineering & Physical Science Research Council (EPSRC)
Royal Academy Of Engineering
Grant Number
EP/K034332/1
RF/129
Subjects
Science & Technology
Technology
Microscopy
forescatter electron imaging
metallurgy
microscopy
titanium
transmission Kikuchi diffraction
variant selection
ELECTRON BACKSCATTER DIFFRACTION
SPATIAL-RESOLUTION
DWELL-FATIGUE
EBSD
DEFORMATION
PATTERNS
SIZE
MICROSCOPE
GRAIN
cond-mat.mtrl-sci
0204 Condensed Matter Physics
0912 Materials Engineering
0601 Biochemistry And Cell Biology
Publication Status
Published