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Using transmission Kikuchi diffraction to characterise α variants in an α+β titanium alloy.
J Microsc. 2017 09; 267(3):318-329.JM

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.

Authors+Show Affiliations

Department of Materials, Royal School of Mines, Imperial College London, Kensington, London, SW7 2AZ, UK.Department of Materials, Royal School of Mines, Imperial College London, Kensington, London, SW7 2AZ, UK.Department of Materials, Royal School of Mines, Imperial College London, Kensington, London, SW7 2AZ, UK.Department of Materials, Royal School of Mines, Imperial College London, Kensington, London, SW7 2AZ, UK.Department of Materials, Royal School of Mines, Imperial College London, Kensington, London, SW7 2AZ, UK.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

28470948

Citation

Tong, V, et al. "Using Transmission Kikuchi Diffraction to Characterise Α Variants in an Α+β Titanium Alloy." Journal of Microscopy, vol. 267, no. 3, 2017, pp. 318-329.
Tong V, Joseph S, Ackerman AK, et al. Using transmission Kikuchi diffraction to characterise α variants in an α+β titanium alloy. J Microsc. 2017;267(3):318-329.
Tong, V., Joseph, S., Ackerman, A. K., Dye, D., & Britton, T. B. (2017). Using transmission Kikuchi diffraction to characterise α variants in an α+β titanium alloy. Journal of Microscopy, 267(3), 318-329. https://doi.org/10.1111/jmi.12569
Tong V, et al. Using Transmission Kikuchi Diffraction to Characterise Α Variants in an Α+β Titanium Alloy. J Microsc. 2017;267(3):318-329. PubMed PMID: 28470948.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Using transmission Kikuchi diffraction to characterise α variants in an α+β titanium alloy. AU - Tong,V, AU - Joseph,S, AU - Ackerman,A K, AU - Dye,D, AU - Britton,T B, Y1 - 2017/05/04/ PY - 2016/12/20/received PY - 2017/03/22/revised PY - 2017/03/25/accepted PY - 2017/5/5/pubmed PY - 2017/5/5/medline PY - 2017/5/5/entrez KW - forescatter electron imaging KW - metallurgy KW - microscopy KW - titanium KW - transmission Kikuchi diffraction KW - variant selection SP - 318 EP - 329 JF - Journal of microscopy JO - J Microsc VL - 267 IS - 3 N2 - 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. SN - 1365-2818 UR - https://www.unboundmedicine.com/medline/citation/28470948/Using_transmission_Kikuchi_diffraction_to_characterise_α_variants_in_an_α+β_titanium_alloy_ L2 - https://doi.org/10.1111/jmi.12569 DB - PRIME DP - Unbound Medicine ER -
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