196,191 research outputs found
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/
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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Dry sliding wear behaviour of powder metallurgy Al-Mg-Si alloy-MoSi2 composites and the relationship with the microstructure
Get PDFThe effect of the microstructure on the dry sliding wear of six aluminium alloy 6061 matrix composites reinforced with 15 vol.% of MoSi2 particles and two monolithic 6061 alloys processed by powder metallurgy with and without ball milling has been studied. Wear testing was undertaken using pin-on-ring configuration against an M2 steel counterface at 0.94 m/s and normal load of 42, 91 and 140 N. The wear resistance of the aluminium alloys was significantly improved by ball milling and the addition of reinforcing MoSi2 particles due to a more stable and more homogeneous microstructure, which avoids the detachment of the mechanically mixed layer. Wear rate of materials in T6 decreases as solutionized hardness of the materials increases. This behaviour is rationalized by taking into account the precipitation state of the matrix. In addition, wear rate follows a Hall–Petch type relationship, showing that the reduction of matrix grain size plays an important role in the increase in the wear resistance of the composites. The results indicate that the present intermetallic reinforced composites can be considered potential substitutes for ceramic reinforced aluminium alloys in tribological applications
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
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
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