Imperial College London

Dr T Ben Britton

Faculty of EngineeringDepartment of Materials

Reader in Metallurgy and Microscopy
 
 
 
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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

117 results found

Tong VS, Ben Britton T, 2021, TrueEBSD: Correcting spatial distortions in electron backscatter diffraction maps, Ultramicroscopy, Vol: 221, Pages: 1-8, ISSN: 0304-3991

Electron backscatter diffraction (EBSD) in the scanning electron microscope is routinely used for microstructural characterisation of polycrystalline materials. Maps of EBSD data are typically acquired at high stage tilt and slow scan speed, leading to tilt and drift distortions that obscure or distort features in the final microstructure map. In this paper, we describe TrueEBSD, an automatic postprocessing procedure for distortion correction with pixel-scale precision. Intermediate images are used to separate tilt and drift distortion components and fit each to a physically-informed distortion model. We demonstrate TrueEBSD on three case studies (titanium, zirconium and hydride containing Zr), where distortion removal has enabled characterisation of otherwise inaccessible microstructural features.

Journal article

Xu Y, Gu T, Xian J, Giuliani F, Britton T, Gourlay C, Dunne Fet al., 2021, Intermetallic size and morphology effects on creep rate of Sn-3Ag-0.5Cu solder, International Journal of Plasticity, Vol: 137, ISSN: 0749-6419

The creep behaviour of directionally solidified SAC305 (96.5Sn-3Ag-0.5Cu wt%) alloy has been investigated with integrated particle matrix composite (PMC) crystal plasticity modelling and quantitative experimental characterisation and test. In this manuscript, the mechanistic basis of creep rate dependence is shown to be influenced by plastic strain gradients, and the associated hardening due to geometrically necessary dislocation (GND) density. These gradients are created due to heterogenous deformation at the Sn phase and intermetallic compound (IMCs) boundaries. The size and distribution of IMCs is important, as finer and well dispersed IMCs leading to higher creep resistance and lower creep rates, and this agrees with experimental observations. This understanding has enabled the creation of a new microstructurally homogenized model which captures this mechanistic link between the GND hardening, the intermetallic size, and the corresponding creep rate. The homogenised model relates creep rates to the microstructure found within the solder alloy as they evolve in service, when ageing and coarsening kinetics are known.

Journal article

Gu T, Gourlay CM, Britton TB, 2021, The Role of Lengthscale in the Creep of Sn-3Ag-0.5Cu Solder Microstructures, Journal of Electronic Materials, ISSN: 0361-5235

<jats:title>Abstract</jats:title><jats:p>Creep of directionally solidified Sn-3Ag-0.5Cu wt.% (SAC305) samples with near-&lt;110&gt; orientation along the loading direction and different microstructural lengthscale is investigated under constant load tensile testing and at a range of temperatures. The creep performance improves by refining the microstructure, i.e. the decrease in secondary dendrite arm spacing (<jats:italic>λ</jats:italic><jats:sub>2</jats:sub>), eutectic intermetallic spacing (<jats:italic>λ</jats:italic><jats:sub><jats:italic>e</jats:italic></jats:sub>) and intermetallic compound (IMC) size, indicating a longer creep lifetime, lower creep strain rate, change in activation energy (<jats:italic>Q</jats:italic>) and increase in ductility and homogeneity in macro- and micro-structural deformation of the samples. The dominating creep mechanism is obstacle-controlled dislocation creep at room temperature and transits to lattice-associated vacancy diffusion creep at elevated temperature (<jats:inline-formula><jats:alternatives><jats:tex-math>$$ \frac{T}{{T_{M} }} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mfrac> <mml:mi>T</mml:mi> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>M</mml:mi> </mml:msub> </mml:mfrac> </mml:math></jats:alternatives></jats:inline-formula> &gt; 0.7 to 0.75). The deformation mechanisms are investigated using electron backscatter diffraction and strain heterogeneity is identified between <jats:italic>β</jats:italic>-Sn in dendrites and <jats:italic>β</jats:italic>-Sn in eutectic region

Journal article

Mouton I, Chang Y, Chakraborty P, Wang S, Stephenson LT, Ben Britton T, Gault Bet al., 2021, Hydride growth mechanism in Zircaloy-4: investigation of the partitioning of alloying elements, Materialia, Pages: 101006-101006, ISSN: 2589-1529

Journal article

McAuliffe TP, Dye D, Britton TB, 2020, Spherical-angular dark field imaging and sensitive microstructural phase clustering with unsupervised machine learning., Ultramicroscopy, Vol: 219, Pages: 1-11, ISSN: 0304-3991

Electron backscatter diffraction is a widely used technique for nano- to micro-scale analysis of crystal structure and orientation. Backscatter patterns produced by an alloy solid solution matrix and its ordered superlattice exhibit only extremely subtle differences, due to the inelastic scattering that precedes coherent diffraction. We show that unsupervised machine learning (with principal component analysis, non-negative matrix factorisation, and an autoencoder neural network) is well suited to fine feature extraction and superlattice/matrix classification. Remapping cluster average patterns onto the diffraction sphere lets us compare Kikuchi band profiles to dynamical simulations, confirm the superlattice stoichiometry, and facilitate virtual imaging with a spherical solid angle aperture. This pipeline now enables unparalleled mapping of exquisite crystallographic detail from a wide range of materials within the scanning electron microscope.

Journal article

Wang S, Giuliani F, Britton T, 2020, Slip-hydride interactions in Zircaloy-4: Multiscale mechanical testing and characterisation, Acta Materialia, Vol: 200, Pages: 537-550, ISSN: 1359-6454

The interactions between δ-hydrides and plastic slip in a commercial zirconium alloy, Zircaloy-4, under load were studied using in situ secondary electron microscope (SEM) micropillar compression tests of single crystal samples and ex situ digital image correlation (DIC) macroscale tensile tests of polycrystalline samples. The hydrides decorate near basal planes in orientation, and for micropillars orientated for 〈a〉 basal slip localised shear at the hydride–matrix interface is favoured over slip in α-Zr matrix due to a lower shear stress required. In contrast, for pillars oriented for 〈a〉 prismatic slip the shear stress needed to trigger plastic slip within the hydride is slightly higher than the critical resolved shear stress (CRSS) for the 〈a〉 prismatic slip system. In this case, slip in the hydride is likely achieved through 〈110〉-type shear which is parallel to the activated 〈a〉-type shear in the parent matrix. At a longer lengthscale, these results are used to inform polycrystalline samples analysed using high spatial resolution DIC. Here localised interface shear remains to be a significant deformation path which can both cause and be caused by matrix slip on planes closely-oriented to the phase boundaries. Matrix slip on planes nearly perpendicular to the adjacent hydride–matrix interfaces can either result in plastic slip within the hydrides or get arrested at the interfaces, generating local stress concentration. Through these mechanisms, the presence of δ-hydrides leads to enhanced strain localisation in Zircaloy-4 early in the plastic regime.

Journal article

Gu T, Tong V, Gourlay C, Britton Tet al., 2020, In-situ study of creep in Sn-3Ag-0.5Cu solder, Acta Materialia, Vol: 196, Pages: 31-43, ISSN: 1359-6454

The creep behaviour and microstructural evolution of a Sn-3Ag-0.5Cu wt% sample with a columnar microstructure have been investigated through in-situ creep testing under constant stress of 30 MPa at ~298 K. This is important, as 298 K is high temperature within the solder system and in-situ observations of microstructure evolution confirm the mechanisms involved in deformation and ultimately failure of the material. The sample has been observed in-situ using repeat and automatic forescatter diode and auto electron backscatter diffraction imaging. During deformation, polygonisation and recrystallisation are observed heterogeneously with increasing strain, and these correlate with local lattice rotations near matrix-intermetallic compound interfaces. Recrystallised grains have either twin or special boundary relationships to their parent grains. The combination of these two imaging methods reveal grain 1 (loading direction, LD, 10.4° from [100]) deforms less than the neighbour grain 2 (LD 18.8° from [110]), with slip traces in the strain localised regions. In grain 2, (10)[001] slip system is observed and in grain 1 (10)[1]/2 and (110)[11]/2 slip systems are observed. Lattice orientation gradients build up with increasing plastic strain and near fracture recrystallisation is observed concurrent with fracture.

Journal article

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

Pedrazzini S, Pek ME, Ackerman AK, Ali H, Ghadbeigi H, Mumtaz K, Dessolier T, Britton TB, Bajaj P, Jägle E, Gault B, London AJ, Galindo-Nava Eet al., 2020, Influence of powder-bed temperature on the microstructure and mechanical properties of Ti-6Al-4V produced by selective laser melting, Publisher: arXiv

Advanced characterisation techniques were used on LPBF Ti-6Al-4V samplesproduced on a heated base plate. When the substrate temperature is 100{\deg}Cthe elongation is 6\%, which increases and peaks at 10\% at 570{\deg}C, thensharply decreases to zero ductility at 770{\deg}C. At 100{\deg}C, a heavilystrained and twinned microstructure, primarily composed of {\alpha}+{\alpha}',was observed and it was comparable to asbuilt microstructures obtained byconventional LPBF methods. At higher temperatures, twins are no longer presentand instead nano-scale {\beta} precipitates are observed within {\alpha}' and{\alpha}, as well as dislocation networks (570{\deg}C) and tangles(770{\deg}C). Solute segregation at crystal defects was observed in allpre-heating conditions. Al and V segregation at microtwins was observed in the100{\deg}C sample, reporting for the first time `selective' and mutuallyexclusive Al- and V-rich regions forming in adjacent twins. V segregation atdislocations was observed in the 570{\deg}C and 770{\deg}C samples, consistentwith the higher preheating temperatures. High O contents were measured in allsamples but with apparent opposing effects. At 100{\deg}C and 570{\deg}C wasestimated to be below the critical threshold for O embrittlement and locallyaids in maintaining a strength high by solid solution strengthening, whereas at770{\deg}C it was above the threshold, therefore failing in a brittle fashion.Based on these observations, the initial increase in ductility from 100{\deg}Cto 570{\deg}C is attributed to a reduction in microtwins and the dislocationnetworks acting as `soft barriers' for slip within a coarser microstructure.The lack of ductility at 770{\deg}C was attributed to local soluteredistribution causing dislocation pinning and an increase of O content in thissample.

Working paper

Ball P, Hengel E, Moriarty P, Oliver R, Rippon G, Britton T, Saini A, Wade Jet al., 2020, 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 T-S, Sernicola G, Ben Britton T, 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, ISSN: 2589-1529

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, 2019, 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., 2019, 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

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