ORCID Profile
0000-0002-4588-6007
Current Organisations
Imperial College London
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Publisher: IEEE
Date: 09-2018
Publisher: Japan Institute of Metals
Date: 2008
Publisher: Springer Science and Business Media LLC
Date: 28-09-2013
Publisher: Iron and Steel Institute of Japan
Date: 2013
Publisher: IEEE
Date: 05-2015
Publisher: Iron and Steel Institute of Japan
Date: 2013
Publisher: MDPI AG
Date: 31-01-2022
DOI: 10.3390/MET12020266
Abstract: Manganese-bearing intermetallic compounds (IMCs) are important for ensuring adequate corrosion performance of magnesium-aluminium alloys and can be deleterious to mechanical performance if they are large and/or form clusters. Here, we explore the formation of Al-Mn IMCs in Mg-9Al-0.7Zn-0.2Mn produced by two industrial casting processes, high-pressure die casting (HPDC) and direct chill (DC) casting. As Al8Mn5 starts forming above the α-Mg liquidus temperature in this alloy, we consider its formation during melt handling as well as during casting and heat treatment. In HPDC, we focus on sludge formation in the holding pot, partial solidification of IMCs in the shot chamber, and Al-Mn IMC solidification in the die cavity. In DC casting, we focus on interactions between Al-Mn IMCs and oxide films in the launder system, Al-Mn IMC solidification in the billet, and the partial transformation of Al8Mn5 into Al11Mn4 during solution heat treatment. The results show that minimising pre-solidification in the shot sleeve of HPDC and controlling pouring and filtration in DC casting are important for ensuring small Al-Mn intermetallic particles in these casting processes.
Publisher: Trans Tech Publications, Ltd.
Date: 10-2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/SSP.192-193.179
Abstract: Optimising semi-solid processing and accurately modelling semi-solid deformation requires a fundamental understanding of the globule-scale mechanisms that cause the macroscopic rheological response. In this work, apparatus and analysis techniques are being developed for the time-resolved, three-dimensional imaging of semi-solid alloy deformation. This paper overviews synchrotron X-ray tomography results on globular Al-15wt%Cu deformed at 0.7 solid fraction using extrusion. The globule-globule interactions in response to load were quantified in terms of the response of in idual globules with respect to globule translation, rotation, and deformation. The potential of time-resolved X-ray tomography in the study of semi-solid alloy deformation is then discussed.
Publisher: Elsevier BV
Date: 03-2019
Publisher: IOP Publishing
Date: 11-06-2015
Publisher: Springer Science and Business Media LLC
Date: 12-04-2019
Publisher: Elsevier BV
Date: 09-2020
Publisher: Springer Science and Business Media LLC
Date: 27-01-2023
DOI: 10.1007/S11661-022-06937-2
Abstract: Eutectic Ag 3 Sn can grow with a variety of morphologies depending on the solidification conditions and plays an important role in the performance of Pb-free solders. Here, we study morphology transitions in the β -Sn + Ag 3 Sn eutectic at increasing growth velocity using a combination of real-time X-ray imaging and analytical electron microscopy. Orthorhombic Ag 3 Sn grew as faceted plates or rods with [010] growth direction and (001) as the largest facet in all three eutectic growth morphologies: Irregular plate, broken-lamellar, and rod. Reproducible β -Sn + Ag 3 Sn orientation relationships formed for the latter two morphologies. The mechanisms of spacing adjustment and the reversible transition from plate to rod growth are studied for transient solidification after velocity changes. The transition from fully eutectic growth to β -Sn dendrites plus eutectic is reasonably reproduced using a competitive growth criterion. At the highest velocities, Ag 3 Sn rods developed perturbations whose break down into particles is discussed in terms of unsteady growth and pinch-off mechanisms.
Publisher: Springer Science and Business Media LLC
Date: 18-07-2014
DOI: 10.1038/NCOMMS5464
Abstract: The behaviour of granular solid–liquid mixtures is key when deforming a wide range of materials from cornstarch slurries to soils, rock and magma flows. Here we demonstrate that treating semi-solid alloys as a granular fluid is critical to understanding flow behaviour and defect formation during casting. Using synchrotron X-ray tomography, we directly measure the discrete grain response during uniaxial compression. We show that the stress–strain response at 64–93% solid is due to the shear-induced dilation of discrete rearranging grains. This leads to the counter-intuitive result that, in unfed s les, compression can open internal pores and draw the free surface into the liquid, resulting in cracking. A soil mechanics approach shows that, irrespective of initial solid fraction, the solid packing density moves towards a constant value during deformation, consistent with the existence of a critical state in mushy alloys analogous to soils.
Publisher: AIP Publishing
Date: 08-02-2010
DOI: 10.1063/1.3310019
Abstract: We investigate how 5 at. % Ni influences the relative stability of η and η′ Cu6Sn5. Synchrotron x-ray diffraction shows that, while Cu6Sn5 exists as η′ at 25 and 150 °C and transforms to η on heating to 200 °C, Cu5.5Ni0.5Sn5 is best fit to η throughout 25–200 °C. Our first principles calculations predict that η′ is stable at T=0 K in both Cu6Sn5 and Cu5.5Ni0.5Sn5, but that the energy difference is substantially reduced from 1.21 to 0.90 eV per 22 atom cell by the Ni addition. This effect is attributed to Ni developing distinct bonding to both Cu and Sn in the η phase.
Publisher: Elsevier BV
Date: 12-2005
Publisher: Elsevier BV
Date: 10-2014
Publisher: Springer Science and Business Media LLC
Date: 05-12-2018
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 06-2011
Publisher: Springer Science and Business Media LLC
Date: 22-10-2015
Publisher: Springer Science and Business Media LLC
Date: 13-11-2010
Publisher: Springer Science and Business Media LLC
Date: 19-09-2008
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 08-2017
Publisher: Springer Science and Business Media LLC
Date: 13-02-2015
DOI: 10.1038/SREP08450
Abstract: Hydrogen has the potential to power much of the modern world with only water as a by-product, but storing hydrogen safely and efficiently in solid form such as magnesium hydride remains a major obstacle. A significant challenge has been the difficulty of proving the hydriding/dehydriding mechanisms and, therefore, the mechanisms have long been the subject of debate. Here we use in situ ultra-high voltage transmission electron microscopy (TEM) to directly verify the mechanisms of the hydride decomposition of bulk MgH 2 in Mg-Ni alloys. We find that the hydrogen release mechanism from bulk (2 μm) MgH 2 particles is based on the growth of multiple pre-existing Mg crystallites within the MgH 2 matrix, present due to the difficulty of fully transforming all Mg during a hydrogenation cycle whereas, in thin s les analogous to nano-powders, dehydriding occurs by a ‘shrinking core’ mechanism.
Publisher: Springer Science and Business Media LLC
Date: 04-12-2017
DOI: 10.1038/S41467-017-01727-6
Abstract: While many aspects of electronics manufacturing are controlled with great precision, the nucleation of tin in solder joints is currently left to chance. This leads to a widely varying melt undercooling and different crystal orientations in each joint, which results in a different resistance to electromigration, thermomechanical fatigue, and other failure modes in each joint. Here we identify a family of nucleants for tin, prove their effectiveness using a novel droplet solidification technique, and demonstrate an approach to incorporate the nucleants into solder joints to control the orientation of the tin nucleation event. With this approach, it is possible to change tin nucleation from a stochastic to a deterministic process, and to generate single-crystal joints with their c -axis orientation tailored to best combat a selected failure mode.
Publisher: Elsevier BV
Date: 05-2018
Publisher: Trans Tech Publications, Ltd.
Date: 10-2012
DOI: 10.4028/WWW.SCIENTIFIC.NET/SSP.192-193.185
Abstract: Synchrotron radiography experiments are overviewed that directly image semi-solid deformation at the globule-scale. Globular Al-15Cu at 50-60% solid was deformed in direct-shear at 10-2 s-1. Deformation is shown to occur by globule rearrangement without discernible deformation of the in idual globules. Globules were found to translate and rotate as quasi-discrete bodies in response to forces acting at globule-globule contacts, similar to liquid-saturated granular materials such as water-saturated sand. Rearrangement caused the globule packing-density (the solid fraction) to adjust by local compaction and local dilation of the globule assembly, and deformation is highly inhomogeneous. During shear, there was a net dilation and strain began to localize into a shear band of decreased solid fraction by the end of the experiments.
Publisher: IEEE
Date: 05-2015
Publisher: Springer Science and Business Media LLC
Date: 06-07-2007
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 06-2013
Publisher: Elsevier BV
Date: 09-2009
Publisher: Elsevier BV
Date: 06-2015
Publisher: Springer Science and Business Media LLC
Date: 30-10-2018
Publisher: Elsevier BV
Date: 06-2020
Publisher: Springer Science and Business Media LLC
Date: 06-02-2020
DOI: 10.1038/S41467-020-14453-3
Abstract: In-depth understanding of microstructure development is required to fabricate high quality products by additive manufacturing (for ex le, 3D printing). Here we report the governing role of side-branching in the microstructure development of alloys by laser powder bed fusion. We show that perturbations on the sides of cells (or dendrites) facilitate crystals to change growth direction by side-branching along orthogonal directions in response to changes in local heat flux. While the continuous epitaxial growth is responsible for slender columnar grains confined to the centreline of melt pools, side-branching frequently happening on the sides of melt pools enables crystals to follow drastic changes in thermal gradient across adjacent melt pools, resulting in substantial broadening of grains. The variation of scan pattern can interrupt the vertical columnar microstructure, but promotes both in-layer and out-of-layer side-branching, in particular resulting in the helical growth of microstructure in a chessboard strategy with 67° rotation between layers.
Publisher: Japan Welding Society
Date: 2009
DOI: 10.2207/JJWS.78.600
Publisher: Springer Science and Business Media LLC
Date: 13-10-2020
DOI: 10.1007/S11664-020-08498-9
Abstract: The coarsening of Ag 3 Sn particles occurs during the operation of joints and plays an important role in failure. Here, Ag 3 Sn coarsening is studied at 125°C in the eutectic regions of Sn-3Ag-0.5Cu/Cu solder joints by SEM-based time-lapse imaging. Using multi-step thresholding segmentation and image analysis, it is shown that coalescence of Ag 3 Sn particles is an important ripening process in addition to LSW-like Ostwald ripening. About 10% of the initial Ag 3 Sn particles coalesced during ageing, coalescence occurred uniformly across eutectic regions, and the scaled size distribution histograms contained large particles that can be best fit by the Takajo model of coalescence ripening. Similar macroscopic coarsening kinetics were measured between the surface and bulk Ag 3 Sn particles. Tracking of in idual surface particles showed an interplay between the growth/shrinkage and coalescence of Ag 3 Sn.
Publisher: IEEE
Date: 04-2017
Publisher: Trans Tech Publications, Ltd.
Date: 07-2016
DOI: 10.4028/WWW.SCIENTIFIC.NET/KEM.700.142
Abstract: Sn-3Ag-3Bi-3In solder has been investigated to improve the understanding of microstructure formation in this solder during solidification and soldering to Cu and Ni substrates. The as-solidified microstructures of Sn-3Ag-3Bi-3In s les were found to consist of a significant fraction of βSn dendrites with a complex eutectic between the dendrites. In total five phases were observed to form during solidification: βSn, Ag 3 Sn, Bi, ζAg and a “Sn-In-Bi” ternary compound. Soldering of Sn-3Ag-3Bi-3In to substrates changed the phase equilibria in the system and caused the formation of additional phases: Cu 6 Sn 5 during soldering to Cu and Ni 3 Sn 4 and metastable NiSn 4 during soldering to Ni. It is shown that metastable NiSn 4 forms as a primary phase in a complex 5-component Sn-3Ag-3Bi-3In-Ni system. In and Bi were detected in solid solution in the βSn matrix in amounts of ~1.5-2at% and ~1.2at% respectively. Bi also existed as fine particles of two distinct types. (i): sub-micron ( nm) coral-like particles and (ii) facetted particles measuring up to 7-8 μm.
Publisher: IEEE
Date: 04-2019
Publisher: Springer Science and Business Media LLC
Date: 10-2009
Publisher: Springer Science and Business Media LLC
Date: 09-2004
Publisher: Springer Science and Business Media LLC
Date: 21-09-2008
Publisher: Springer Science and Business Media LLC
Date: 12-01-2017
DOI: 10.1038/SREP40010
Abstract: The development of microstructure during melting, reactive wetting and solidification of solder pastes on Cu-plated printed circuit boards has been studied by synchrotron radiography. Using Sn-3.0Ag-0.5Cu/Cu and Sn-0.7Cu/Cu as ex les, we show that the interfacial Cu 6 Sn 5 layer is present within 0.05 s of wetting, and explore the kinetics of flux void formation at the interface between the liquid and the Cu 6 Sn 5 layer. Quantification of the nucleation locations and anisotropic growth kinetics of primary Cu 6 Sn 5 crystals reveals a competition between the nucleation of Cu 6 Sn 5 in the liquid versus growth of Cu 6 Sn 5 from the existing Cu 6 Sn 5 layer. Direct imaging confirms that the β-Sn nucleates at/near the Cu 6 Sn 5 layer in Sn-3.0Ag-0.5Cu/Cu joints.
Publisher: Elsevier BV
Date: 06-2011
Publisher: Springer Science and Business Media LLC
Date: 18-08-2015
Publisher: Elsevier BV
Date: 03-2022
Publisher: IOP Publishing
Date: 03-07-2012
Publisher: Informa UK Limited
Date: 02-11-2015
Publisher: Elsevier BV
Date: 12-2005
Publisher: Elsevier BV
Date: 12-2009
Publisher: Informa UK Limited
Date: 2004
Publisher: Elsevier BV
Date: 06-2017
Publisher: Trans Tech Publications, Ltd.
Date: 04-2018
DOI: 10.4028/WWW.SCIENTIFIC.NET/SSP.273.66
Abstract: Sn-0.7Cu-0.05Ni is a widely used Pb-free solder that solidifies into a near-eutectic microstructure and a small fraction of primary Cu 6 Sn 5 . This paper overviews in-situ time-resolved imaging experiments on the solidification of Sn-0.7Cu-0.05Ni solder under three conditions: (i) directional solidification, (ii) continuous cooling in a near-uniform thermal field, and (iii) solder joint solidification on a Cu substrate. Primary Cu 6 Sn 5 grow as rods along [0001] in each case but can also grow as X-shaped crystals in (iii). There are significant differences in eutectic growth due to nucleation difficulties for tin in conditions (ii) and (iii).
Publisher: Elsevier BV
Date: 09-2021
Publisher: IEEE
Date: 11-2016
Publisher: Trans Tech Publications, Ltd.
Date: 07-2008
DOI: 10.4028/WWW.SCIENTIFIC.NET/SSP.141-143.337
Abstract: This paper studies the conditions under which strain localisation occurs in partially solid alloys and compares localisation in rheology experiments with features in the industrial processes of Thixomolding® and high pressure die casting (HPDC). To study the fundamentals of localisation, vane rheometry, modified to measure volumetric changes, is used to shear magnesium alloy AZ91 during solidification. Deformation is found to readily localise when the initial microstructure consists of an assembly of crystals in contact. It is shown that such microstructures expand as they are sheared due to Reynolds’ dilatancy, and that localisation takes the form of dilatant shear bands. A study of microstructural features in industrial castings demonstrates that similar dilatant shear bands can form during Thixomoulding® and HPDC.
Publisher: Springer Science and Business Media LLC
Date: 21-03-2021
DOI: 10.1007/S11661-021-06213-9
Abstract: Multi-axial compression of the mushy zone occurs in various pressurized casting processes. Here, we present a drained triaxial compression apparatus for semi-solid alloys that allow liquid to be drawn into or expelled from the s le in response to isotropic or triaxial compression. The rig is used to measure the pressure-dependent flow stress and volumetric response during isothermal triaxial compression of globular semi-solid Al-15 wt pct Cu at 70 to 85 vol pct solid. Analysis of the stress paths and the stress–volume data show that the combination of the solid fraction and mean effective pressure determines whether the material undergoes shear-induced dilation or contraction. The results are compared with the critical state soil mechanics (CSSM) framework and the similarities and differences in behavior between equiaxed semi-solid alloys and soils are discussed.
Publisher: IEEE
Date: 09-2018
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 08-2022
Publisher: Springer Science and Business Media LLC
Date: 03-2005
Publisher: Elsevier BV
Date: 2017
Publisher: IOP Publishing
Date: 03-07-2012
Publisher: Elsevier BV
Date: 05-2011
Publisher: Springer Science and Business Media LLC
Date: 14-08-2014
Publisher: Elsevier BV
Date: 03-2020
Publisher: Elsevier BV
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 15-10-2020
DOI: 10.1007/S11664-020-08508-W
Abstract: The microstructure of Sn-Ag-Cu (SAC) solder joints plays an important role in the reliability of electronics, and interlaced twinning has been linked with improved performance. Here, we study the three-dimensional (3-D) shape of interlaced regions in Sn-3.0Ag-0.5Cu (SAC305) solder balls by combining serial sectioning with electron backscatter diffraction. In solder balls without large Ag 3 Sn plates, we show that the interlaced volume can be reasonably approximated as a hollow double cone with the common 〈100〉 twinning axis as the cone axis, and the 〈110〉 from all three twinned orientations making up the cone sides. This 3-D morphology can explain a range of partially interlaced morphologies in past work on 2-D cross-sections.
Publisher: Elsevier BV
Date: 11-2011
Publisher: Springer Science and Business Media LLC
Date: 28-04-2009
Publisher: Springer Science and Business Media LLC
Date: 17-06-2014
Publisher: Springer International Publishing
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 11-03-2020
Publisher: Elsevier BV
Date: 10-2016
Publisher: IEEE
Date: 04-2017
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 08-2017
Publisher: Elsevier BV
Date: 04-2022
Publisher: Elsevier BV
Date: 08-2016
Publisher: Trans Tech Publications, Ltd.
Date: 05-2016
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.857.44
Abstract: The solidification of Sn-3Ag-0.5Cu and Sn-0.7Cu-0.05Ni are overviewed and compared. In joints on Cu substrates, both solders begin solidification with primary Cu 6 Sn 5 growing in the bulk liquid prior to tin nucleation. In freestanding balls and joints, SAC305 generally solidifies with a single tin nucleation event and exhibits a mutually-twinned tin grain structure. In contrast, SN100C BGA balls and joints exhibit multiple independent tin grains that grow as a columnar array in joints.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Springer Science and Business Media LLC
Date: 06-09-2017
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 08-2018
Publisher: Springer International Publishing
Date: 2018
Publisher: Wiley
Date: 24-09-2023
Publisher: Elsevier BV
Date: 07-2020
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 07-2018
Publisher: IEEE
Date: 04-2018
Publisher: Elsevier BV
Date: 07-2023
Publisher: Elsevier BV
Date: 08-2008
Publisher: Trans Tech Publications, Ltd.
Date: 06-2010
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.654-656.1367
Abstract: The influence of external mechanical stresses on agglomeration and bending of solidifying crystals has been investigated by microstructural characterisation of hypoeutectic Al cast specimens. The s les were produced by near-static cooling, gravity die casting and high pressure die casting (HPDC), where the solidifying crystals experience different levels of mechanical stresses. Electron backscatter diffraction (EBSD) technique was used to acquire grain misorientation data which can be linked to crystal agglomeration and bending behaviour during solidification. The length fraction of low-energy grain boundaries in HPDC s les was substantially higher than in gravity diecast and ‘statically cooled’ s les. This is related to the high amount of shear applied on the solidifying alloy, which promotes crystal collisions and agglomeration. In-grain misorientations were significant only in branched dendritic crystals which were subjected to significant shear stresses. This is attributed to the increased bending moment acting on long, protruding dendrite arms compared to more compact crystal morphologies.
Publisher: Elsevier BV
Date: 02-2017
Publisher: Elsevier BV
Date: 12-2017
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 07-2011
Publisher: Elsevier BV
Date: 12-2010
Publisher: Trans Tech Publications, Ltd.
Date: 04-2009
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.618-619.607
Abstract: This article focuses on the influence of intensification pressure (I.P.) on the feeding through the gate during high pressure die casting (HPDC). Two values of intensification pressure, the lowest and highest possible for the HPDC machine used, were applied to cast AlSi3MgMn tensile-bar specimens. The castings produced with higher I.P. contained a lower total fraction of porosity, as expected. Microstructural characterisation of the gate region showed markedly different features in and adjacent to the gate at the two levels of I.P. used. The microstructures indicate a change in feeding mechanism with increasing I.P. At high I.P. shear band-like features exist through the gate, suggesting that strain localisation in the gate is involved in the feeding of solidification shrinkage during the I.P. stage. At low I.P. such shear bands were not observed in the gates and feeding was less effective, resulting in a higher level of porosity in the HPDC parts.
Publisher: Elsevier BV
Date: 06-2012
Publisher: Springer Science and Business Media LLC
Date: 06-2009
Publisher: Springer International Publishing
Date: 2017
Publisher: IOP Publishing
Date: 03-07-2012
Publisher: Elsevier BV
Date: 11-2018
Publisher: IEEE
Date: 04-2016
Publisher: Springer Science and Business Media LLC
Date: 17-06-2014
Publisher: Springer Science and Business Media LLC
Date: 26-10-2020
DOI: 10.1007/S11664-020-08507-X
Abstract: Antimony is attracting interest as an addition to Pb-free solders to improve thermal cycling performance in harsher conditions. Here, we investigate microstructure evolution and failure in harsh accelerated thermal cycling (ATC) of a Sn-3.8Ag-0.9Cu solder with 5.5 wt.% antimony as the major addition in two ball grid array (BGA) packages. SbSn particles are shown to precipitate on both Cu 6 Sn 5 and as cuboids in β-Sn, with reproducible orientation relationships and a good lattice match. Similar to Sn-Ag-Cu solders, the microstructure and damage evolution were generally localised in the β-Sn near the component side where localised β-Sn misorientations and subgrains, accelerated SbSn and Ag 3 Sn particle coarsening, and β-Sn recrystallisation occurred. Cracks grew along the network of recrystallised grain boundaries to failure. The improved ATC performance is mostly attributed to SbSn solid-state precipitation within β-Sn dendrites, which supplements the Ag 3 Sn that formed in a eutectic reaction between β-Sn dendrites, providing populations of strengthening particles in both the dendritic and eutectic β-Sn.
Publisher: Elsevier BV
Date: 10-2011
Publisher: Springer Science and Business Media LLC
Date: 23-10-2012
Publisher: Elsevier BV
Date: 04-2017
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 05-2006
Publisher: IEEE
Date: 12-2015
Publisher: Elsevier BV
Date: 2020
Publisher: Springer Science and Business Media LLC
Date: 27-04-2010
Publisher: IOP Publishing
Date: 11-06-2015
Publisher: Elsevier BV
Date: 2010
Publisher: Trans Tech Publications, Ltd.
Date: 10-2007
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.561-565.1067
Abstract: Transitions in the mechanical behaviour of solidifying alloys influence feeding mechanisms and defect formation during many casting processes. This paper explores dendrite coherency and the cracking transition during the equiaxed dendritic solidification of Mg alloy AZ91 using the continuous-torque technique and vane rheometry. The two techniques yielded similar dendrite coherency values of ~17% solid, and the cracking transition occurred at 40% solid in vane rheometry tests. These transition values are similar to those reported for Al alloys with equiaxed dendritic morphology and a similar grain size.
Publisher: IOP Publishing
Date: 12-01-2012
Publisher: Elsevier BV
Date: 06-2013
Publisher: Elsevier BV
Date: 03-2023
Publisher: Elsevier BV
Date: 03-2017
Publisher: Springer Science and Business Media LLC
Date: 03-2005
Publisher: Springer Science and Business Media LLC
Date: 16-01-2021
DOI: 10.1007/S11664-020-08697-4
Abstract: Creep of directionally solidified Sn-3Ag-0.5Cu wt.% (SAC305) s les with near- 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 ( λ 2 ), eutectic intermetallic spacing ( λ e ) and intermetallic compound (IMC) size, indicating a longer creep lifetime, lower creep strain rate, change in activation energy ( Q ) and increase in ductility and homogeneity in macro- and micro-structural deformation of the s les. The dominating creep mechanism is obstacle-controlled dislocation creep at room temperature and transits to lattice-associated vacancy diffusion creep at elevated temperature ( $$ \\frac{T}{{T_{M} }} $$ T T M 0.7 to 0.75). The deformation mechanisms are investigated using electron backscatter diffraction and strain heterogeneity is identified between β -Sn in dendrites and β -Sn in eutectic regions containing Ag 3 Sn and Cu 6 Sn 5 particles. The size of the recrystallised grains is modulated by the dendritic and eutectic spacings however, the recrystalised grains in the eutectic regions for coarse-scaled s les (largest λ 2 and λ e ) is only localised next to IMCs without growth in size.
Publisher: Elsevier BV
Date: 2019
Publisher: Springer Science and Business Media LLC
Date: 16-10-2015
Publisher: Springer Science and Business Media LLC
Date: 20-08-2015
Publisher: Springer Science and Business Media LLC
Date: 2007
DOI: 10.1038/NATURE05426
Abstract: Compacted granular materials expand in response to shear, and can exhibit different behaviour from that of the solids, liquids and gases of which they are composed. Application of the physics of granular materials has increased the understanding of avalanches, geological faults, flow in hoppers and silos, and soil mechanics. During the equiaxed solidification of metallic alloys, there exists a range of solid fractions where the microstructure consists of a geometrically crowded disordered assembly of crystals saturated with liquid. It is therefore natural to ask if such a microstructure deforms as a granular material and what relevance this might have to solidification processing. Here we show that partially solidified alloys can exhibit the characteristics of a cohesionless granular material, including Reynolds' dilatancy and strain localization in dilatant shear bands 7-18 mean crystals wide. We show that this behaviour is important in defect formation during high pressure die casting of Al and Mg alloys, a global industry that contributes over $7.3 billion to the USA's economy alone and is used in the manufacture of products that include mobile-phone covers and steering wheels. More broadly, these findings highlight the potential to apply the principles and modelling approaches developed in granular mechanics to the field of solidification processing, and also indicate the possible benefits that might be gained from exploring and exploiting further synergies between these fields.
Publisher: Springer Science and Business Media LLC
Date: 07-04-2017
DOI: 10.1038/SREP43720
Abstract: In a comment on our Article “Evidence of the hydrogen release mechanism in bulk MgH 2 ”, Surrey et al . assert that the MgH 2 s le we studied was not MgH 2 at any time but rather MgO and that the transformation we observed was the formation of Kirkendall voids due to the outward diffusion of Mg. We address these issues in this reply.
Publisher: Springer Science and Business Media LLC
Date: 31-10-2018
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2015
End Date: 2022
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2014
End Date: 2019
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2013
End Date: 2017
Funder: Engineering and Physical Sciences Research Council
View Funded ActivityStart Date: 2010
End Date: 2012
Funder: Engineering and Physical Sciences Research Council
View Funded Activity