Imperial College London

Dr T Ben Britton

Faculty of EngineeringDepartment of Materials

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 2634b.britton Website

 
 
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Location

 

B301Bessemer BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

107 results found

McGilvery C, Jiang J, Rounthwaite N, Williams R, Giuliani F, Britton Tet al., 2020, Characterisation of carbonaceous deposits on diesel injector nozzles, Fuel: the science and technology of fuel and energy, Vol: 274, Pages: 1-9, ISSN: 0016-2361

Diesel injector nozzles are highly engineered components designed to optimise delivery of fuel into the combustion chamber of modern engines. These components contain narrow channels to enhance spray formation and penetration, hence mixing and combustion. Over time, these injectors can become clogged due to fouling by carbonaceous deposits which may affect the long-term performance of a diesel engine. In this paper we explore the chemical composition and structure of deposits formed within the nozzle at the nanometre scale using electron microscopy. We focus on comparing deposits generated using a chassis dynamometer-based test with Zn fouled fuel with a DW10B dirty up test. We have developed and applied a method to precisely section the deposits for ‘top view’ scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis of the morphology and relative accumulation of deposits formed during chassis dynamometer and engine based dirty-up tests. We extend this analysis to finer length scales through lift-out of ~70 nm thick electron transparent cross section foils, including both the metal substrate and deposit, using focussed ion beam (FIB) machining. These foils are analysed using scanning transmission electron microscopy (STEM) and STEM-EDS. These thin foils reveal thin-film growth and chemical stratification of Zn, C, O and other elements in the organic deposit layers developed during growth on the steel substrate during industry standard fouling tests.

Journal article

Kyvelou P, Slack H, Daskalaki Mountanou D, Wadee MA, Britton T, Buchanan C, Gardner Let al., 2020, Mechanical and microstructural testing of wire and arc additivelymanufactured sheet material, Materials and Design, Vol: 192, ISSN: 0264-1275

Wire and arc additive manufacturing (WAAM) is a method of 3D printing that enables large elements to be built, with reasonable printing times and costs. There are, however, uncertainties relating to the structural performance of WAAM material, including the basic mechanical properties, the degree of anisotropy, the influence of the as-built geometry and the variability in response. Towards addressing this knowledge gap, a comprehensive series of tensile tests on WAAM stainless steel was conducted; the results are presented herein. As-built and machined coupons were tested to investigate the influence of the geometrical irregularity on the stress-strain characteristics, while material anisotropy was explored by testing coupons produced at different angles to the printing orientation. Non-contact measurement techniques were employed to determine the geometric properties and deformation fields of the specimens, while sophisticated analysis methods were used for post processing the test data. The material response revealed a significant degree of anisotropy, explained by the existence of a strong crystallographic texture, uncovered by means of electron backscatter diffraction. Finally, the effective mechanical properties of the as-built material were shown to be strongly dependent on the geometric variability; simple geometric measures were therefore developed to characterise the key aspects of the observed behaviour.

Journal article

Ball P, Hengel E, Moriarty P, Oliver R, Rippon G, Britton T, Saini A, Wade Jet al., Gender issues in fundamental physics: Strumia's bibliometric analysis fails to account for key confounders and confuses correlation with causation, Quantitative Science Studies, ISSN: 2641-3337

Alessandro Strumia recently published a survey of gender differences in publications and citations in high-energy physics (HEP). In addition to providing full access to the data, code, and methodology, Strumia (2020) systematically describes and accounts for gender differences in HEP citation networks. His analysis points both to ongoing difficulties in attracting women to high-energy physics and an encouraging—though slow—trend in improvement.

Journal article

Bhowmik A, Lee J, Adande S, Wang-Koh M, Jun TS, Sernicola G, Britton TB, Rae CMF, Balint D, Giuliani Fet al., 2020, Investigating spatio-temporal deformation in single crystal Ni-based superalloys using in-situ diffraction experiments and modelling, Materialia, Vol: 9

© 2020 In this study, we perform a detailed analysis of room temperature deformation of a [100]–orientated single crystal Ni-based superalloy, CMSX-4 micropillar, using a combinatorial and complimentary characterisation approach of micro-Laue diffraction coupled with post-deformation microscopy and crystal plasticity modelling. Time-resolved micro-Laue data indicated that deformation was initiated by activation of multiple slip (after 5% engineering strain) which led to the generation of a plastic strain accumulation accompanied by a two-fold increase in the dislocation density within the micropillar. Subsequent to that, slip occurred primarily on two systems (11¯1)[101] and (111)[1¯01] with the highest Schmid factor in the single crystal micropillar thereby resulting in little accumulation of unpaired GNDs during a major part of the loading cycle, upto 20% strain in this case. Finite element crystal plasticity modelling also showed good agreement with the experimental analyses, whereby significant strains were found to develop in the above slip systems with a localisation near the centre of the micropillar. Post-deformation transmission electron microscopy study confirmed that deformation was mediated through a/2<110> dislocations on {111} planes in the γ-phase, while high stress levels led to shearing of the γ′ precipitates by a/2<110> partials bounding an anti-phase boundary free to glide on the {111} planes. During the deformation of the single crystal micropillar, independent rotations of the γ and γ′ phases were quantified by spatially resolved post-deformation micro-Laue patterns. The degree of lattice rotation in the γ-phase was higher than that in the γ′-phase.

Journal article

McAuliffe TP, Foden A, Bilsland C, Daskalaki Mountanou D, Dye D, Britton TBet al., 2020, Advancing characterisation with statistics from correlative electron diffraction and X-ray spectroscopy, in the scanning electron microscope., Ultramicroscopy, Vol: 211, Pages: 1-16, ISSN: 0304-3991

The routine and unique determination of minor phases in microstructures is critical to materials science. In metallurgy alone, applications include alloy and process development and the understanding of degradation in service. We develop a correlative method, exploring superalloy microstructures, which are examined in the scanning electron microscope (SEM) using simultaneous energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD). This is performed at an appropriate length scale for characterisation of carbide phases' shape, size, location, and distribution. EDS and EBSD data are generated using two different physical processes, but each provide a signature of the material interacting with the incoming electron beam. Recent advances in post-processing, driven by 'big data' approaches, include use of principal component analysis (PCA). Components are subsequently characterised to assign labels to a mapped region. To provide physically meaningful signals, the principal components may be rotated to control the distribution of variance. In this work, we develop this method further through a weighted PCA approach. We use the EDS and EBSD signals concurrently, thereby labelling each region using both EDS (chemistry) and EBSD (crystal structure) information. This provides a new method of amplifying signal-to-noise for very small phases in mapped regions, especially where the EDS or EBSD signal is not unique enough alone for classification.

Journal article

Gu T, Xu Y, Gourlay CM, Britton TBet al., 2020, In-situ electron backscatter diffraction of thermal cycling in a single grain Cu/Sn-3Ag-0.5Cu/Cu solder joint, Scripta Materialia, Vol: 175, Pages: 55-60, ISSN: 1359-6462

The heterogeneous evolution of microstructure in a single grain Cu/SAC305/Cu solder joint is investigated using in-situ thermal cycling combined with electron backscatter diffraction (EBSD). Local deformation due to thermal expansion mismatch results in heterogeneous lattice rotation within the joint, localised towards the corners. This deformation is induced by the constraint and the coefficient of thermal expansion (CTE) mismatch between the β-Sn, Cu6Sn5 and Cu at interfaces. The formation of subgrains with continuous increase in misorientation is revealed during deformation, implying the accumulation of plastic slip at the strain-localised regions and the activation of slip systems (110)[11]/2 and (0)[111]/2.

Journal article

Guo Y, Collins DM, Tarleton E, Hofmann F, Wilkinson AJ, Ben Britton Tet al., 2020, Dislocation density distribution at slip band-grain boundary intersections, ACTA MATERIALIA, Vol: 182, Pages: 172-183, ISSN: 1359-6454

Journal article

Foden A, Collins DM, Wilkinson AJ, Britton TBet al., 2019, Indexing electron backscatter diffraction patterns with a refined template matching approach, Publisher: ELSEVIER

Working paper

Wang S, Kalacska S, Maeder X, Michler J, Giuliani F, Ben Britton Tet al., 2019, The effect of delta-hydride on the micromechanical deformation of a Zr alloy studied by in situ high angular resolution electron backscatter diffraction, Publisher: PERGAMON-ELSEVIER SCIENCE LTD

Working paper

Hielscher R, Bartel F, Britton TB, 2019, Gazing at crystal balls: Electron backscatter diffraction pattern analysis and cross correlation on the sphere, Ultramicroscopy, Vol: 207, Pages: 1-11, ISSN: 0304-3991

We present spherical analysis of electron backscatter diffraction (EBSD) patterns with two new algorithms: (1) band localisation and band profile analysis using the spherical Radon transform; (2) orientation determination using spherical cross correlation. These new approaches are formally introduced and their accuracies are determined using dynamically simulated patterns. We demonstrate their utility with an experimental dataset obtained from ferritic iron. Our results indicate that the analysis of EBSD patterns on the sphere provides an elegant method of revealing information from these rich sources of crystallographic data.

Journal article

Hielscher R, Bartel F, Britton TB, Gazing at crystal balls - Electron backscatter diffraction indexing and cross correlation on a sphere, Ultramicroscopy, ISSN: 0304-3991

We present spherical analysis of electron backscatter diffraction (EBSD)patterns with two new algorithms: (1) pattern indexing utilising a sphericalRadon transform and band localisation; (2) pattern indexing with directspherical cross correlation on the surface of the sphere, with refinement.These new approaches are formally introduced and their accuracies aredetermined using dynamically simulated patterns. We demonstrate their utilitywith an experimental dataset obtained from ferritic iron. Our results indicatethat analysis of EBSD patterns on the surface of a sphere provides a valuablemethod of unlocking information from these rich sources of crystallographicdata.

Journal article

Wang S, Kalácska S, Maeder X, Michler J, Giuliani F, Britton Tet al., The effect of δ-hydride on the micromechanical deformation of Zircaloy-4 studied by in situ high angular resolution electron backscatter diffraction, Scripta Materialia, ISSN: 1359-6462

Zircaloy-4(Zr-1.5%Sn-0.2%Fe-0.1%Cr wt%)is usedas nuclear fuel cladding materials and hydride embrittlementis amajor failure mechanism. To explore the effect of δ-hydrideon plastic deformation and performance of Zircaloy-4, in situhigh angular resolution electron backscatter diffraction(HR-EBSD)was used to quantify stress andgeometrically necessarydislocation(GND)density during bending tests of hydride-free and hydride-containingsingle crystalZircaloy-4 microcantilevers. Results suggest that while the stress applied was accommodated by plastic slip in the hydride-free cantilever,the hydride-containing cantilever showedprecipitation-induced GND pile-up at hydride-matrix interfacepre-deformation, andconsiderable locally-increasing GNDdensity under tensile stressupon plastic deformation.

Journal article

Britton B, Jackson C, Wade J, 2019, The reward and risk of social media for academics, Nature Reviews Chemistry, Vol: 3, Pages: 459-461, ISSN: 2397-3358

We are three academics who are active on social media. We explore the motivations for and benefits of engaging with social media, as well as its costs and risks. Overall, we believe this engagement to be a net benefit for us, our employers and for wider society.

Journal article

Wallis D, Hansen LN, Britton TB, Wilkinson AJet al., 2019, High-angular resolution electron backscatter diffraction as a new tool for mapping lattice distortion in geological minerals, Journal of Geophysical Research. Solid Earth, Vol: 124, Pages: 6337-6358, ISSN: 2169-9356

Analysis of distortions of the crystal lattice within individual mineralgrains is central to the investigation of microscale processes that control andrecord tectonic events. These distortions are generally combinations of latticerotations and elastic strains, but a lack of suitable observational techniqueshas prevented these components being mapped simultaneously and routinely inearth science laboratories. However, the technique of high-angular resolutionelectron backscatter diffraction (HR-EBSD) provides the opportunity tosimultaneously map lattice rotations and elastic strains with exceptionalprecision, on the order of 0.01 degree for rotations and 10-4 in strain, usinga scanning electron microscope. Importantly, these rotations and latticestrains relate to densities of geometrically necessary dislocations andresidual stresses. Recent works have begun to apply and adapt HR-EBSD togeological minerals, highlighting the potential of the technique to provide newinsights into the microphysics of rock deformation. Therefore, the purpose ofthis overview is to provide a summary of the technique, to identify caveats andtargets for further development, and to suggest areas where it offers potentialfor major advances. In particular, HREBSD is well suited to characterising theroles of different dislocation types during crystal plastic deformation and tomapping heterogeneous internal stress fields associated with specificdeformation mechanisms/microstructures or changes in temperature, confiningpressure, or applied deviatoric stress. These capabilities make HR-EBSD aparticularly powerful new technique for analysing the microstructures ofdeformed geological materials.

Journal article

Gianola DS, Britton TB, Zaefferer S, 2019, New techniques for imaging and identifying defects in electron microscopy, MRS Bulletin, Vol: 44, Pages: 450-458, ISSN: 0883-7694

Defects in crystalline solids control the properties of engineered and natural materials, and their characterization focuses our strategies to optimize performance. Electron microscopy has served as the backbone of our understanding of defect structure and their interactions, owing to beneficial spatial resolution and contrast mechanisms that enable direct imaging of defects. These defects reside in complex microstructures and chemical environments, demanding a combination of experimental approaches for full defect characterization. In this article, we describe recent progress and trends in methods for examining defects using scanning electron microscopy platforms. Several emerging approaches offer attractive benefits, for instance, in correlative microscopy across length scales and in in situ studies of defect dynamics.

Journal article

Wang S, Giuliani F, Britton TB, 2019, Microstructure and formation mechanisms of δ-hydrides in variable grain size Zircaloy-4 studied by electron backscatter diffraction, Acta Materialia, Vol: 169, Pages: 76-87, ISSN: 1359-6454

Microstructure and crystallography of δ phase hydrides in as-received fine grain and ‘blocky alpha’ large grain Zircaloy-4 (average grain size ∼11 μm and >200 μm, respectively) were examined using electron backscatter diffraction (EBSD). Results suggest that the matrix-hydride orientation relationship is {0001} α ||{111} δ ;<112¯0> α ||<110> δ for all the cases studied. The habit plane of intragranular hydrides and some intergranular hydrides has been found to be {101¯7} of the surrounding matrix. The morphology of intergranular hydrides can vary depending upon the angle between the grain boundary and the hydride habit plane. The misfit strain between α-Zr and δ-hydride is accommodated mainly by high density of dislocations and twin structures in the hydrides, and a mechanism of twin formation in the hydrides has been proposed. The growth of hydrides across grain boundaries is achieved through an auto-catalytic manner similar to the growth pattern of intragranular hydrides. Easy collective shear along <11¯00> makes it possible for hydride nucleation at any grain boundaries, while the process seems to favour grain boundaries with low (<40°) and high (>80°) c-axis misorientation angles. Moreover, the angle between the grain boundary and the adjacent basal planes does not influence the propensity for hydride nucleation.

Journal article

Moutona I, Breen AJ, Wang S, Chang Y, Szczepaniak A, Kontis P, Stephenson LT, Raabe D, Herbig M, Britton TB, Gault Bet al., 2019, Quantification challenges for atom probe tomography of hydrogen and deuterium in zircaloy-4, Microscopy and Microanalysis, Vol: 25, Pages: 481-488, ISSN: 1431-9276

Analysis and understanding of the role of hydrogen in metals is a significant challenge for the future of materials science, and this is a clear objective of recent work in the atom probe tomography (APT) community. Isotopic marking by deuteration has often been proposed as the preferred route to enable quantification of hydrogen by APT. Zircaloy-4 was charged electrochemically with hydrogen and deuterium under the same conditions to form large hydrides and deuterides. Our results from a Zr hydride and a Zr deuteride highlight the challenges associated with accurate quantification of hydrogen and deuterium, in particular associated with the overlap of peaks at a low mass-to-charge ratio and of hydrogen/deuterium containing molecular ions. We discuss possible ways to ensure that appropriate information is extracted from APT analysis of hydrogen in zirconium alloy systems that are important for nuclear power applications.

Journal article

Wang S, Giuliani F, Britton T, 2019, Variable temperature micropillar compression to reveal <a> basal slip properties of Zircaloy-4, Scripta Materialia, Vol: 162, Pages: 451-455, ISSN: 1359-6462

Zircaloy-4 is widely used as nuclear fuel cladding materials, where it is important to understand the mechanical properties between room temperature and reactor operating temperatures (around 623 K). To aid in this understanding, we have performed compression tests on micropillars aligned to activate <a> basal slip across this temperature range. Engineering analysis of the results indicates that the plastic yield follows a thermally activated constitutive law. We also observe the nature of the slip bands formed on the side surface of our pillars and see characteristic ‘bulging’ that tends to localise as temperature increases.

Journal article

Winkelmann A, Ben Britton T, Nolze G, 2019, Constraints on the effective electron energy spectrum in backscatter Kikuchi diffraction, Publisher: AMER PHYSICAL SOC

Working paper

Jun T-S, Maeder X, Bhowmik A, Guillonneau G, Michler J, Giuliani F, Britton TBet al., 2019, The role of β-titanium ligaments in the deformation of dual phase titanium alloys, Materials Science and Engineering: A, Vol: 746, Pages: 394-405, ISSN: 0921-5093

Multiphase titanium alloys are critical materials in high value engineeringcomponents, for instance in aero engines. Microstructural complexity isexploited through interface engineering during mechanical processing to realisesignificant improvements in fatigue and fracture resistance and strength. Inthis work, we explore the role of select interfaces using in-situmicromechanical testing with concurrent observations from high angularresolution electron backscatter diffraction (HR-EBSD). Our results aresupported with post mortem transmission electron microscopy (TEM). Usingmicro-pillar compression, we performed in-depth analysis of the role of select{\beta}-titanium (body centred cubic) ligaments which separate neighbouring{\alpha}-titanium (hexagonal close packed) regions and inhibit the dislocationmotion and impact strength during mechanical deformation. These results shedlight on the strengthening mechanisms and those that can lead to strainlocalisation during fatigue and failure.

Journal article

Gu T, Gourlay C, Britton T, 2019, Evaluating creep deformation in controlled microstructures of Sn-3Ag-0.5Cu solder, Journal of Electronic Materials, Vol: 48, Pages: 107-121, ISSN: 0361-5235

The reliability of solder joints is affected significantly by thermomechanical properties such as creep and thermal fatigue. In this work, the creep of directionally solidified (DS) Sn-3Ag-0.5Cu wt.% (SAC305) dog-bone samples (gauge dimension: 10 × 2 × 1.5 mm) with a controlled <110> or <100> fibre texture is investigated under constant load testing (stress level: ∼ 30 MPa) at a range of temperatures from 20°C to 200°C. Tensile testing is performed and the secondary creep strain rate and the localised strain gradient are studied by two-dimensional optical digital image correlation (2-D DIC). The dominating creep mechanisms and their temperature dependence are explored at the microstructural scale using electron backscatter diffraction (EBSD), which enables the understanding of the microstructural heterogeneity of creep mechanisms at different strain levels, temperatures and strain rates. Formation of subgrains and the development of recrystallization are observed with increasing strain levels. Differences in the deformation of β-Sn in dendrites and in the eutectic regions containing Ag3Sn and Cu6Sn5 are studied and related to changes in local deformation mechanisms.

Journal article

Tong VS, Knowles AJ, Dye D, Ben Britton Tet al., 2019, Rapid electron backscatter diffraction mapping: Painting by numbers, Materials Characterization, Vol: 147, Pages: 271-279, ISSN: 1044-5803

Microstructure characterisation has been greatly enhanced through the use of electron backscatter diffraction (EBSD), where rich maps are generated through analysis of the crystal phase and orientation in the scanning electron microscope (SEM). Conventional EBSD analysis involves raster scanning of the electron beam and serial analysis of each diffraction pattern in turn. For grain shape, crystallographic texture, and microstructure analysis this can be inefficient. In this work, we present Rapid EBSD, a data fusion approach combining forescatter electron (FSE) imaging with static sparse sampling of EBSD patterns. We segment the FSE image into regions of similar colour (i.e. phase and crystal orientation) and then collect representative EBSD data for each segmented region. This enables microstructural assessment to be performed at the spatial resolution of the (fast) FSE imaging whilst including orientation and phase information from EBSD analysis of representative points. We demonstrate the Rapid EBSD technique on samples of a cobalt based superalloy and a strained dual phase titanium alloy, comparing the results with conventional analysis. Rapid EBSD is advantageous for assessing grain size distributions in time-limited experiments.

Journal article

Birch R, Wang S, Tong VS, Britton TBet al., 2019, The effect of cooling rate and grain size on hydride microstructure in Zircaloy-4, Journal of Nuclear Materials, Vol: 513, Pages: 221-225, ISSN: 0022-3115

We explore the distribution, morphology and structure of zirconium hydrides formed using different cooling rates through the solid state Zr+[H] → Zr + hydride transus, in fine and blocky alpha Zircaloy-4. We observe that cooling rate and grain size control the phase and distribution of hydrides formed. The blocky alpha (coarse grain, > 200 μm) Zircaloy-4, has a smaller grain boundary area to grain volume ratio and this significantly affects nucleation and growth of hydrides as compared to fine grain size (∼11 μm) material.

Journal article

Britton TB, Tong V, Hickey J, Foden A, Wilkinson Aet al., 2018, AstroEBSD: exploring new space in pattern indexing with methods launched from an astronomical approach, Journal of Applied Crystallography, Vol: 51, Pages: 1525-1534, ISSN: 0021-8898

Electron backscatter diffraction (EBSD) is a technique used to measure crystallographic features in the scanning electron microscope. The technique is highly automated and readily accessible in many laboratories. EBSD pattern indexing is conventionally performed with raw electron backscatter patterns. These patterns are software processed to locate the band centres (and sometimes edges) from which the crystallographic index of each band is determined. Once a consistent index for many bands is obtained, the crystal orientation with respect to a reference sample and detector orientation can be determined and presented. Unfortunately, because of challenges related to crystal symmetry, there are limited available pattern-indexing approaches and this has probably hampered open development of the technique. In this article, a new method of pattern indexing is presented, based upon a method with which satellites locate themselves in the night sky, and its effectiveness is systematically demonstrated using dynamical simulations and real experimental patterns. The benefit of releasing this new algorithm as open-source software is demonstrated when this indexing process is utilized, together with dynamical solutions, to provide some of the first accuracy assessments of an indexing solution. In disclosing a new indexing algorithm, and software processing toolkit, the authors hope to open up EBSD developments to more users. The software code and example data are released alongside this article for third party developments.

Journal article

Breen AJ, Mouton I, Lu W, Wang S, Szczepaniak A, Kontis P, Stephenson LT, Chang Y, da Silva AK, Liebscher C, Raabe D, Britton TB, Herbig M, Gault Bet al., 2018, Atomic scale analysis of grain boundary deuteride growth front in Zircaloy-4, Scripta Materialia, Vol: 156, Pages: 42-46, ISSN: 1359-6462

Zircaloy-4 (Zr-1.5%Sn-0.2%Fe-0.1%Cr wt%) was electrochemically charged with deuterium to create deuterides and subsequently analysed with atom probe tomography and scanning transmission electron microscopy to understand zirconium hydride formation and embrittlement. At the interface between the hexagonal close packed (HCP) α-Zr matrix and a face centred cubic (FCC) δ deuteride (ZrD1.5–1.65), a HCP ζ phase deuteride (ZrD0.25–0.5) has been observed. Furthermore, Sn is rejected from the deuterides and segregates to the deuteride/α-Zr reaction front.

Journal article

Lan B, Britton TB, Jun T-S, Gan W, Hofmann M, Dunne F, Lowe Met al., 2018, Direct volumetric measurement of crystallographic texture using acoustic waves, Acta Materialia, Vol: 159, Pages: 384-394, ISSN: 1359-6454

Crystallographic texture in polycrystalline materials is often developed as preferred orientation distribution of grains during thermo-mechanical processes. Texture dominates many macroscopic physical properties and reflects the histories of structural evolution, hence its measurement and control are vital for performance optimisation and deformation history interogation in engineering and geological materials. However, exploitations of texture are hampered by state-of-the-art characterisation techniques, none of which can routinely deliver the desirable non-destructive, volumetric measurements, especially at larger lengthscales. Here we report a direct and general methodology retrieving important lower-truncation-order texture and phase information from acoustic (compressional elastic) wave speed measurements in different directions through the material volume (avoiding the need for forward modelling). We demonstrate its deployment with ultrasound in the laboratory, where the results from seven representative samples are successfully validated against measurements performed using neutron diffraction. The acoustic method we have developed includes both fundamental wave propagation and texture inversion theories which are free from diffraction limits, they are arbitrarily scalable in dimension, and can be rapidly deployed to measure the texture of large objects. This opens up volumetric texture characterisation capabilities in the areas of material science and beyond, for both scientific and industrial applications.

Journal article

Luan Q, Britton TB, Jun T, 2018, Strain rate sensitivity in commercial pure titanium: the competition between slip and deformation twinning, Materials Science and Engineering: A, Vol: 734, Pages: 385-397, ISSN: 0921-5093

Titanium alloys are widely used in light weight applications such as jet engine fans, where their mechanical performance under a range of loading regimes is important. Titanium alloys are mechanically anisotropic with respect to crystallographic orientation, and remarkably titanium creeps at room temperature. This means that the strain rate sensitivity (SRS) and stress relaxation performance are critical in predicting component life. In this work, we focus on systematically exploring the macroscopic SRS of Grade 1 commercially pure titanium (CP Ti) with varying grain sizes and texture using uniaxial compression. Briefly, we find that Ti samples had positive SRS and samples compressed along the sheet rolling direction (RD) (i.e. soft grains dominant) were less rate sensitive than bars compressed along the sheet normal direction (ND) (i.e. hard grains dominant). We attribute this rate sensitivity to the relative activity of slip and twinning. Within the grain size range of ~ 317 ±7 μm, we observe an increase in the rate sensitivity, where volume fraction of {101 ̅2}<101 ̅1> T1 tensile twins was low, and the twin width at different strain rates were similar. These observations imply that the macroscopic rate sensitivity is controlled by the ensemble behaviour of local deformation processes: the amount of slips accumulated at grain boundaries affects the SRS, which is grain size and texture dependent. We hope that this experimental study motivates mechanistic modelling studies using crystal plasticity, including strain rate sensitivity and twinning, to predict the performance of titanium alloys.

Journal article

Niania M, Podor R, Britton TB, Li C, Cooper SJ, Svetkov N, Skinner S, Kilner Jet al., 2018, In situ study of strontium segregation in La<inf>0.6</inf>Sr<inf>0.4</inf>Co<inf>0.2</inf>Fe<inf>0.8</inf>O<inf>3- δ</inf>in ambient atmospheres using high-temperature environmental scanning electron microscopy, Journal of Materials Chemistry A, Vol: 6, Pages: 14120-14135, ISSN: 2050-7496

Samples of the solid oxide fuel cell cathode material La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF) were annealed using High-Temperature Environmental Scanning Electron Microscopy (HT-ESEM) from room temperature to 1000 °C in atmospheres of pure oxygen, pure water and ambient lab air. Image series of each heat treatment were taken where microstructural changes were observed and compared between samples. Strontium segregation rate was found to be significantly increased in the presence of pure water as compared to pure O2and ambient air. Electron backscattered diffraction (EBSD) was performed in order to assess the effect of crystal orientation on particle formation and surface sensitive chemical analysis techniques were used to determine the chemical changes at the grain surface as a result of the different heat treatments. It was shown that crystal orientation affected the nature and growth rate of strontium-based particles, however, due to the pseudo-symmetry of La0.6Sr0.4Co0.2Fe0.8O3-δ, precise crystal orientation relationships could not be determined. The chemical composition of the grain surface was found to be approximately equal under each atmosphere.

Journal article

Britton TB, Goran D, Tong VS, 2018, Space rocks and optimising scanning electron channelling contrast, Materials Characterization, Vol: 142, Pages: 422-431, ISSN: 1044-5803

Forescatter electron imaging is a popular microscopy technique, especially for scanning electron microscopes equipped with an electron backscatter diffraction detector. In principal, this method enables qualitative imaging of microstructure but quantitative assessment can be limited due to limited information about the contrast afforded. In this work, we explore forescatter electron imaging and demonstrate that imaging can be optimised for topographic, phase, and subtle orientation contrast imaging through appropriate sample and detector positioning. We demonstrate the relationship between imaging modes using systematic variation in detector positioning and compare this with pseudo-forescatter electron images, obtained from image analysis of diffraction patterns, to explore and confirm image contrast modes. We demonstrate these contrast mechanisms on a map obtained from a sample of the Gibeon meteorite.

Journal article

Niania M, Podor R, Britton TB, Li C, Cooper SJ, Svetkov N, Skinner S, Kilner Jet al., 2018, Correction: In situ study of strontium segregation in La<inf>0.6</inf>Sr<inf>0.4</inf>Co<inf>0.2</inf>Fe<inf>0.8</inf>O<inf>3- δ</inf>in ambient atmospheres using high-temperature environmental scanning electron microscopy (J. Mater. Chem. A (2018) DOI: 10.1039/c8ta01341a), Journal of Materials Chemistry A, Vol: 6, Pages: 14464-14464, ISSN: 2050-7488

© 2018 The Royal Society of Chemistry. Correction for 'In situ study of strontium segregation in La0.6Sr0.4Co0.2Fe0.8O3-δin ambient atmospheres using high-temperature environmental scanning electron microscopy' by Mathew Niania et al., J. Mater. Chem. A, 2018, DOI: 10.1039/c8ta01341a. The authors regret that the name of the first author of ref. 37 was displayed as "F. Pisigkin". The correct name should be "F. Piskin". The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

Journal article

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