1,720,991 research outputs found
Effect of al addition on martensitic transformation stability and microstructural and mechanical properties of cuzr based shape memory alloys
No full textIn this work, the effect of the Al content (x = 5, 10, and 15 at. %) on the martensitic transformation (MT) and microstructure and mechanical properties of Cu(50−x)Zr50Alx alloys was studied. The microstructure of the alloys was characterized at room temperature by means of scanning electron microscopy and X-ray diffraction. An increase in Al content reduces the amount of transforming CuZr phase, and consequently the secondary phase formation is favored. The evolution of the MT upon thermal cycling was investigated as a function of the Al content by differential scanning calorimetry. MT temperatures and enthalpies were found to be decreased when increasing the Al content. Al addition can induce a sudden, stable MT below 0◦C, while the binary alloy requires ten complete thermal cycles to stabilize. Finally, the mechanical properties were investigated through microhardness and compression testing. No linear dependence was found with composition. Hardness lowering effect was observed for 5–10 at. % of Al content, while the hardness was increased only for 15 at. % Al addition with respect to the binary alloy. Similarly, compressive response of the alloys showed behavior dependent on the Al content. Up to 10 at. % Al addition, the alloys indicate a superelastic response at room temperature, while higher Al content induced untimely failure
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
Enhanced cryogenic and ambient temperature mechanical properties of CoCuFeMnNi high entropy alloy through controlled heat treatment
No full textDedicated thermal treatments can improve the mechanical behaviour of high entropy alloys (HEAs) by producing nanostructured microstructures with improved characteristics. Herein, the inherent metastability of an equiatomic CoCuFeMnNi alloy was exploited to induce the formation of secondary phases upon ageing treatment. Advanced characterization techniques, namely high resolution synchrotron X-ray diffraction and aberration corrected scanning transmission electron microscopy, allowed to describe the decomposition of the supersaturated solid solution. Nanometric rounded Cu-rich clusters in the solution treated alloy and coherent, regularly oriented Cu-rich discs in the peak-aged condition were possibly produced by spinodal decomposition. An almost 100% enhancement of mechanical strength was obtained thanks to the modulation of composition. Moreover, mechanical behaviour at cryogenic temperature was improved by ageing, both in terms of strength and ductility. Plastic deformation took place by dislocation slip, regardless of the testing temperature.(c) 2022 Elsevier B.V. All rights reserved
Effect of Al and Nb on microstructure and mechanical properties of novel Al-Mo-Nb-Ti-V-Zr lightweight refractory high-entropy alloys
No full textRefractory high-entropy alloys (RHEAs) are a new family of metallic alloys which have been intensively studied in the last decade. Indeed, RHEAs likely have the potential of overcoming the high-temperature performances of conventional Ni-based superalloys. Nevertheless, up to date, their high density and poor room temperature ductility still compromise their industrial uptake. In this study, novel RHEAs compositions are investigated to provide insights on the development of strong and ductile lightweight RHEAs. Specifically, AlxMoNbyTiVZr alloys (with x = 0, 0.25, 0.5, 0.75, 1 and y = 1, 2) have been produced and characterized. These alloys have been designed to probe the possibility of reducing the density of RHEAs by increasing the Al content. At the same time, the content of Nb was also increased in the attempt to counterbalance the embrittlement effect related to Al addition
Development and characterization of a novel high entropy alloy strengthened through concurrent spinodal decomposition and precipitation
Get PDFStrengthening mechanisms, which are commonly exploited by conventional alloys, can be effectively incorporated in high entropy alloys (HEAs) to improve their mechanical behaviour. In this light, compositional modification of equiatomic HEAs can be pursued in order to obtain specific microstructural features. Herein, a face centred cubic CoCuFeMnNi alloy was modified by the addition of a proper amount of Ti; a dedicated thermal treatment allowed to concurrently activate two different phase formation mechanisms, i.e. precipitation and spinodal decomposition. This resulted in a nanostructured microstructure, characterized by the presence of periodic modulations of Cu content and by nanosized coherent L12 Ni3Ti precipitates. Such microstructure resulted in a more than 100 % increase of yield strength after ageing treatment and allowed to retain a satisfactory ductility. Advanced microstructural characterization, coupled with the application of semi-empirical models allowed to understand the role of each microstructural feature in determining the alloy's mechanical strength
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
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