1,720,972 research outputs found
Metallurgical and Mechanical Investigation on Single-Step Quenching and Partitioning Thermal Treatments on Commercial Low Alloyed 30MnV6 Steel
No full textCharacterization of the effect of different Quenching and Partitioning treatments on retained austenite stabilization, on the final microstructure, and on tensile properties was performed on 30MnV6 microalloyed steel. The amount of retained austenite and its location into the final microstructure were evaluated through X-ray diffraction and Electron Backscattered diffraction. Moreover, different initial microstructural conditions were employed to preliminarily investigate the effect of a starting mixed austenite–ferrite microstructure on the effectiveness of the treatment, and to tailor the material final tensile properties according to its actual utilization. Amounts of retained austenite between 4.5 and 6.3 pct were observed. High tensile properties were obtained, reaching 1675 MPa of UTS, with an improved elongation with respect to the reference quenched and tempered condition, which reached 14.8 pct. Hardenability is increased by the presence of retained austenite. Intercritical condition shows lower tensile strength but an increased uniform elongation with respect to the reference quenched and partitioned condition. Therefore, quenching and partitioning appears to be a promising treatment for the selected commercial steel
Strategic approaches to enhance quenching and partitioning applicability: optimizing mechanical properties and microstructure of commercial low-silicon 20MnB5 steel
No full textQuenching and partitioning (QP) is a heat treatment designed to induce a multiphase microstructure composed of martensite and retained austenite. This treatment introduces high tensile properties in the material, coupled with enhanced ductility compared to traditional treatments. This enhancement arises from the strain-induced transformation of retained austenite into martensite when subjected to loads. Austenite stabilization at room temperature is achieved through carbon diffusion from martensite to austenite during partitioning. Therefore, the chemical composition of the alloy is typically tailored to promote this phenomenon. Silicon is added to suppress carbide precipitation, while manganese is added to enhance austenite stability. However, in this study, we focus on commercial low-silicon 20MnB5 steel. This grade is a low-alloyed steel commonly used in the heat-treated condition and is potentially influenced by the properties introduced through QP treatment. Multiple quenching and partitioning treatments are designed and executed to investigate the applicability of QP on 20MnB5 steel. Intercritical treatment strategies are employed to enhance the hardenability of the selected alloy, aiming to prevent bainite transformation and increase the effectiveness of quenching and partitioning, increasing the free carbon at disposal for partitioning. XRD analyses are conducted to identify retained austenite in the final specimen, quantify its amount, and observe its morphology and location. Optical microscopy (OM) and scanning electron microscopy (SEM) are used to characterize the introduced multiphase microstructure. Tensile tests are performed to assess the mechanical properties introduced by the treatment. In conclusion, the study demonstrates the applicability of intercritical quenching and partitioning (QP) treatments on 20MnB5 steel. However, in the observed conditions, the stabilization of a fraction of retained austenite is not correlated to the greatest increase in UE, leading to the conclusion that the control of the surrounding microstructure is the primary factor that influences the final properties of the material
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dynamic Recrystallization Behavior of Low-Carbon Steel during the Flexible Rolling Process: Modeling and Characterization
Full text linkDynamic recrystallization (DRX) is the predominant softening mechanism under high-temperature large-plastic deformation and determines the microstructure evolution of steel. Herein, an equivalent substitution method is proposed to investigate the coupling effect of deformation conditions on microstructural evolution during the flexible rolling process. Low-carbon steel is compressed using a Gleeble 3800-GTC thermal–mechanical physical simulation system at temperatures ranging from 900 to 1100 °C and strain rates ranging from 0.01 to 10 s−1. The flow stress behaviors under different deformation conditions are discussed. Accordingly, the relationship between strain rate and temperature is established using the Zener–Hollomon equation. Further, a new DRX model is proposed by combining the theoretical implications of previous models. The effectiveness of the experimental model and predicted model is statistically evaluated to accurately determine the DRX volume fraction of the experimental steel. Based on the dynamic material model, a hot processing map of the experimental steel is also developed to evaluate the steel's hot workability. Finally, the microstructure of the experimental steel is analyzed under specific deformation parameters. The results demonstrate that DRX behavior decreases as the upper roller is raised and the lower roller is lowered during the flexible rolling process
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Microstructural development via synergic application of Binder jJetting and Quenching and Partitioning (QP) on commercial AISI 4340
No full textThis study investigates the microstructural development of commercial low-alloyed AISI 4340 steel through the synergistic application of Binder Jetting and Quenching and Partitioning (QP) processes. The material in the as-sintered condition exhibited significant variations in microstructure and mechanical properties, primarily influenced by the processing route. Carbon content was influenced by the building technique as decarburization was observed at different intensities mainly during the heating stage of sintering, driven by carbothermic reduction. Vacuum-debinding was found to be optimal, leading to the most homogeneous microstructure, predominantly granular bainite with superior hardness and tensile strength. Different QP treatments were optimized considering the decarburization effect on the optimal as-sintered condition, stabilizing 4–8 % retained austenite in a martensitic matrix, with optimal results observed after isothermal holding at either 220 °C or 240 °C for 30 min. These conditions resulted in high UTS values of 1231 MPa and 1151 MPa, respectively, compared to 750 MPa in the as-sintered state. Despite high tensile properties, A% was limited by the presence of residual porosity. This study highlights the critical importance of controlled debinding and sintering atmospheres as well as decarburization-informed QP treatments in achieving desirable microstructural and mechanical properties in additively manufactured AISI 4340 steel components
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