163 research outputs found
Developing Magnesium Alloys with a Combination of Strength and Ductility Based on Friction Stir-Based Technologies
No full textSome of the key data for the thesis "Developing Magnesium Alloys with a Combination of Strength and Ductility Based on Friction Stir-Based Technologies", including SEM/EDS/EBSD, and TEM data. They are stored in the .oipx format which can be opened by Aztec, .cpr which can be opened by AztecCrystal, and .csv and . tiff as spreadsheets and images.
Part of the data is associated with the following publications:
[1] X. Zhao, X. Zeng, L. Yuan, J. Gandra, Q. Hayat, M. Bai, W.M. Rainforth, D. Guan, A novel approach for producing Mg-3Al-1Zn-0.2 Mn alloy wire with a promising combination of strength and ductility using CoreFlowTM, Scripta Materialia 227 (2023) 115301.
[2] X. Zhao, Y. Xie, J. Gandra, M. Murphy, W.M. Rainforth, D. Guan, A Succinct Method to Recycle WE43 Mg Alloys—From Wasted Chips to Consolidated Billets, TMS Annual Meeting & Exhibition, Springer, (2024), 151-153.
[3] X. Zhao, D. Olden, B. Williams, A. Pariyar, D. Zhang, M. Murphy, P. Reed, P. Allison, B. Jordon, J. Qi, W. M. Rainforth, D. Guan, Grain growth stagnation at 525° C by nanoparticles in a solid-state additively manufactured Mg-4Y-3RE alloy, Journal of Magnesium and Alloys (2024), 4976-4987.
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TEM characterisation of near surface deformation resulting from lubricated sliding wear of aluminium alloy and composites
Get PDFAluminium alloy composites have been extensively investigated for use in tribo-contact applications, however little detailed literature exists on the sub-surface microstructural evolution as a result of lubricated sliding wear. In this study two un-reinforced alloys (2124 and 5056) and identical alloy composites, reinforced with 15 vol.% MoSi2 intermetallic particles were produced by a powder metallurgy route and subject to lubricated sliding at initial Hertzian contact pressures of 0.9–1.2 GPa. Focused ion beam (FIB) techniques were used to produce thin sections parallel to the worn surface. Sub-surfaces layers were then examined in detail by transmission electron microscopy (TEM). Results indicated that the depth of deformation was minimal in the alloys, with the most highly deformed polycrystalline layer confined to approximately 1 ?m below the worn surface. Equiaxed sub-grain sizes of around 0.1 ?m were comparable to that observed for dry sliding of similar alloys and composites [1]. Evidence of surface erosion by solid particle impact was also observed, with wear debris generated as a result of material exceeding the ductility limit. For the composites, the MoSi2 provided a suitable means of transferring the normal contact load from asperity contacts to areas in the bulk of the sample. Reinforcement fracture was observed both at the worn surface and in areas further away in the bulk, for particles which were in direct contact with each other. Evidence of the deformation of the aluminium matrix below reinforcements was also present, with average sub-grain sizes of around 330 nm. Thus, such intermetallic reinforcements may have potential to replace reinforcements that are more abrasive to counterfaces, such as SiC or Al2O3, whilst still providing adequate wear resistance for the aluminium alloy.<br/
Lubricated sliding wear behaviour of aluminium alloy composites
No full textInterest in aluminium alloy (Al-alloy) composites as wear resistant materials continues to grow. However, the use of the popular Al-alloy-SiC composite can be limited by the abrasive nature of the SiC, leading to increased counterface wear rates. This study reports new Al-alloy composites that offer high wear resistance, to a level similar to Al-alloy-SiC. Aluminium alloy (2124, 5056) matrix composites reinforced by nominally 15 vol.% of Cr3Si, MoSi2, Ni3Al and SiC particles were prepared by a powder metallurgy route. The aluminium alloy matrix was produced by gas atomisation, and the Cr3Si, MoSi2 and Ni3Al were prepared by self-propagating high temperature synthesis (SHS), while the SiC was from a standard commercial supply. Following blending, the particulates were consolidated by extrusion, producing a homogenous distribution of the reinforcement in the matrix. Wear testing was undertaken using a pin-on-ring configuration against an M2 steel counterface, with a commercial synthetic oil lubricant, at 0.94 m/s and a normal load of 630 N, corresponding to initial Hertzian contact pressures of 750–890 MPa (the exact value depending on the material properties). Specific wear rates at sliding distances exceeding 400 km were in the range 4.5–12.7 × 10?10 mm3/Nm. The monolithic alloys gave the highest specific wear rates, while the MoSi2 and Cr3Si reinforced alloys exhibited the lowest. The worn surface has been analysed in detail using focused ion beam (FIB) microscopy to determine the sub-surface structural evolution and by tomographic reconstruction of tilted scanning electron microscopy (SEM) images, to determine the local worn surface topography. Consequently, the wear mechanisms as a function of alloy composition and reinforcement type are discussed.<br/
A ‘3-body’ abrasion wear study of bioceramics for total hip-joint replacements
No full textThe current study focuses on the effect of the material type and the lubricant on the abrasive wear behaviour of two important commercially available ceramic on ceramic prosthetic systems, namely, Biolox(R) forte and Bioloxl(R) delta (CeramTec AG, Germany). A standard microabrasion wear apparatus was used to produce '3-body' abrasive wear scars with three different lubricants: ultrapure water, 25 vol% new-born calf serum solution and 1 wt% carboxymethyl cellulose sodium salt (CMC-Na) solution. 1 mu m alumina particles were used as the abrasive. The morphology of the wear scar was examined in detail using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Subsurface damage accumulation was investigated by Focused Ion Beam (FIB) cross-sectional milling and Transmission Electron Microscopy (TEM). The effect of the lubricant on the '3-body' abrasive wear mechanisms is discussed and the effect of material properties compared. (C) 2009 Elsevier B.V. All rights reserved.</p
Insights into tribofilm formation on Ti-6V-4Al in a bioactive environment: Correlation between surface modification and micro-mechanical properties
No full textTi-6Al-4V has been used as a surgical implant material for a long time because of its combination of strength, corrosion resistance and biocompatibility. However, there remains much that is not understood about how the surface reacts with the environment under tribocorrosion conditions. In particular, the conditions under which tribofilms form and their role on friction and wear are not clear. To evaluate the complicated nature of the dynamic surface microstructural changes on the wear track, high resolution transmission electron microscopy (TEM), scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS) have been used to characterise the structure and chemical composition of the tribofilm. Detailed analysis of the formation and structure of the tribofilm and the metal surface deformation behaviour were studied as a function of applied potential and the role of proteins in the lubricant. For the first time, graphitic and onion-like carbon structures from wear debris were found in the testing solution. The presence of carbon nanostructures in the tribocorrosion process and the formation of the tribofilm leads to an improved tribocorrosion behaviour of the system, in particular a reduction in wear and friction. A detailed, quantitative, analysis of surface deformation was undertaken, in particular, the geometrically necessary dislocation (GND) density was quantified using precession electron diffraction (PET). A clear correlation between applied potential, tribofilm formation and the surface strain was established. Statement of significance: The formation of tribofilm and microstructure modification of the Ti-6Al-4V surface during tribocorrosion in a physiological environment is not fully understood. In particular, the correlation between microstructural changes and electrochemical conditions is not clear. This study presents a detailed investigation of the structure and chemical composition of tribofilms at the nanoscale during tribocorrosion tests in simulated body fluid and gives a detailed and quantitative description of the evolved surface structure. A clear correlation between applied potential, tribofilm formation and the surface strain was established. Moreover, particular attention is paid to the wear debris particles captured from the lubricating solution, including nanocarbon onion structures. The implications for tribocorrosion of the alloy in its performance as an implant are discussed.</p
Formation and structure of a subsurface layer in hot rolled aluminium alloy AA3104 transfer bar
No full textAs a basis for extended studies into the evolution, structure and corrosion properties of the subsurface layers in hot rolled aluminium alloys, the evolution of the subsurface layers in industrially rolled AA3104 transfer bar has been simulated in a laboratory mill. Test samples taken from the centre of industrially rolled AA3104 transfer bar were highly polished, reheated and homogenised under carefully determined conditions and rolled in the two-high Robertson mill at the University of Sheffield. The stock surfaces and subsurface layers in industrially rolled and laboratory rolled material were then characterised using a combination of optical microscopy, quantification of stock surface morphology, glow discharge optical emission spectrometry (GDOES), focussed ion beam (FIB) microscopy and filiform corrosion testing. The results from the experimental programme have demonstrated that the near-surface metallic element distributions, the microstructures and depths of the subsurface layers and the filiform corrosion susceptibility of the rolled surfaces in the industrially rolled and laboratory rolled materials were all very similar.<br/
Basal slip mediated tension twin variant selection in magnesium WE43 alloy
No full textTension twinning nucleation and evolution in Mg WE43 alloy over a large sampling area was investigated using a quasi-in-situ EBSD/SEM method during interrupted compression testing. The results showed tension twins with both high and low macroscopic Schmid factor (MSF) were activated under a compressive stress of 100 MPa with a strain rate of 10−1 s−1. Basal slip in most grains dominated at this stress, so nucleation of twin variants required little interaction with non-basal slip, which was different from other studies that reported prismatic slip and/or tension twinning were required to activate some low MSF tension twin variants. The geometric compatibility factor (m') was demonstrated to be an important factor to determine tension twin variant selection assisted by basal slip. The analysis indicated m' played a critical role over MSF in tension twin variant selection during twin nucleation stage, and final twin variant types were insensitive to increasing stress, but they inherited twin variant types determined at twin nucleation stage. Moreover, which specific grain boundary of a grain with hard orientation for basal slip would nucleate which twin variant could be also validated by m' and largely depended on two factors: (a) high value of m' with 1st or 2nd rank between the tension twinning of nucleated twin variant and basal slip in adjoining grains; and (b) intensive basal slip activity in the neighbouring grains before twin nucleation
I dreamt that I dwelt in marble halls [music] : song /
No full textFor voice and piano.; Cover title.; Caption title: The dream.; "Sung by Miss Rainforth at the Theatre Royal Drury Lane in the opera of The Bohemian girl."; Also available online http://nla.gov.au/nla.mus-vn3699059.Bohemian girl. I dreamt that I dwelt in marble hallsDrea
Modelling of formation of stock surface and subsurface layers in breakdown rolling of aluminium alloy
No full textSimulations of the reheating and breakdown rolling of the Al-Mg-Mn aluminium alloy AA3104 carried out using a two-high laboratory mill were supported by detailed numerical modelling of the stock surface layer formation. The model of the stock/roll interface is usually a micro-part of a more complex macro-finite-element model. Corresponding linking of modelling scales is a necessary stage for numerical analysis of fine mechanisms of the interface formation. This procedure allows for consideration of the fine mechanisms responsible for formation of the scale/metal interface while, at the same time, reducing the number of elements under consideration. It has been shown that a small amount of Mg (as oxides) was intermixed into the subsurface layer of a few microns depth by deformation during rolling. The mechanisms which led to the deformation and mixing of the oxide particles into the subsurface layer arose from slip at the roll/stock interface and the action of roll surface asperities on the stock surface.Michal Krzyzanowski, Michael F. Frolish, W. Mark Rainforth, John H. Beyno
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