1,720,967 research outputs found
Novel processing routes for the use of post-consumer aluminum scrap
No full textThe potential for the secondary recycling of aluminum alloys to bridge the gap between current open loop recycling processes and the closed loop processes necessary to establish a circular economy within the aluminum metallurgy sector was evaluated. Six recycling friendly alloys were experimentally developed and their microstructural properties and age hardening responses were characterized, to quantify the impact of recycled contents on typical commercial alloy behaviours.
All alloys were designed to contain estimated typical compositions of aluminum alloys found in scrap yards and were developed using lab-scale casting methods, where 1xxx, 2xxx, 3xxx, 5xxx, 6xxx, and 7xxx series alloys were remelted and cast in an air furnace. Each alloy was comprised of a majority of either AA6111 or AA3003, so these commercial alloys were also cast to serve as baseline comparisons.
The alloys were thermomechanically processed via homogenization heat treatments (1 hour at 560/600°C), hot and cold rolling, quenching, and solution treatments (10 minutes at 560°C). The microstructural evolution during each processing stage was characterized using scanning electron microscopy. Particular emphasis was placed on constituent particle formation to evaluate whether the altered recycled content in the alloys impacted the expected intermetallic phases of their AA6111 or AA3003 base alloys. Energy dispersive x-ray spectroscopy was used to characterize the elemental composition of these particles to determine whether anticipated phases appeared.
The age hardening responses were quantified and evaluated via Vickers micro-hardness measurements. It was determined that two alloys exhibited similar hardening responses as AA6111, therefore, aging curves were developed for all three alloys. They were artificially aged at 0.1, 0.5, 4, 7, 9, 24, and 30.5 hours, and hardness measurements at each time were converted to strength values. A class-based Preciso Precipitation Strengthening Model was developed for each alloy under the assumption that Mg₅Si₆ was the main strengthening phase. The model prediction and Tabor approximations strongly correlated at longer aging times, while the solution treated hardness agreed with a Power Law found in literature.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat
The effect of beam pulsing on laser beam processing of Ti-6Al-4V using a prototype laser additive manufacturing platform
No full textRecent advancements in additive manufacturing have highlighted the limitations of conventional beam motion techniques in manipulating cooling rates and melt pool dynamics. This pursuit has led to the investigation of alternative approaches including multi-beam motion, beam oscillation, beam shaping and beam pulsing, all aimed at refining control over the manufacturing process. Notably, recent research emphasizes the potential benefits of operating in a keyhole regime during laser powder bed additive manufacturing. The primary focus of this research is to provide preliminary insights for our industrial partner (CANMORA TECH Inc.) on the feasibility of beam pulsing as a mechanism for controlling microstructure and particularly defects when melting under conditions that lead to keyholing. The aim is to achieve this control by dynamically adjusting the beam's position over time and modulating power within different duty cycles and frequencies in Laser Powder Bed Additive Manufacturing. The laser tracks are built under these varied pulsing conditions and the results of heat transfer modelling will be presented to predict the impact of pulsing on melt pool geometry.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat
Atomistic simulations of kinetic processes in complex atomic environments
No full textMicrostructure evolution of materials is derived by kinetic processes that are atomistic in nature. Phenomena like grain boundary migration, the formation and growth of crystalline phases in bulk metallic glasses and structural relaxation in amorphous materials are examples of microstructural phenomena that are derived from atomic scale dynamics. Probing such processes in disordered atomic environments is challenging experimentally since they operate at small length scales (nanometers) and time scales (nanoseconds). In this work, we employ molecular dynamics simulations and a variety of dynamical coarse-graining methods to bridge the gap between microscopic processes and macroscopic observables. First, the diffusion kinetics of carbon in Fe-C glasses is studied. By detecting individual atomic hops, we quantify the parameters that control the diffusivity, namely jump length, residence time and correlation factor. Our results help explain the experimentally observed increase in stability of metal-metalloid glasses against crystallization with increasing carbon concentration. Next, the dynamical processes and structural relaxations in a model glassy system are explored using a machine learning algorithm involving neural networks combined with Markov State Models with the aim of identifying previously unexplored dynamical processes that may be crucial for understanding the complex behaviour of metallic glasses. Finally, the kinetic processes governing grain boundary (GB) motion are studied using the same approach as was used for the glasses. The GB mobility is extracted from three GBs in iron using both conventional techniques as well as Markov State Models. The Markov State Model is shown to also provide insights into the intra-GB processes that govern the temperature dependence of GB motion.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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