1,720,959 research outputs found
Effect of different heat treatments on the high temperature tensile behavior and electrical/thermal conductivity of HPDC castings in high recycled content AlSi10MnMg alloy
No full textThe growing need to reduce the carbon footprint of transportation is driving vehicle lightweighting using thin-walled aluminum high-pressure die casting (HPDC) components. Using recycled rather than primary aluminum i.e., from bauxite, further enhances sustainability by reducing energy consumption and emissions. Accordingly, also heat treatments (HTs) with limited energy demand and low risk of dimensional distortions and blistering, like annealing and direct artificial aging, are today preferred. Many HPDC vehicle components also undergo finishing treatments at similar temperatures, such as e-coating, or are exposed to elevate service temperatures that can affect their final properties. Therefore, assessing their strength and thermal management capabilities is critical. The present study investigates the effects of HTs on the high-temperature tensile strength and electrical/thermal conductivity of an automotive component produced from an AlSi10MnMg HPDC alloy with a high recycled content. The mechanical and functional properties are correlated with microstructural features, including the size, morphology, and interparticle spacing of eutectic silicon, as modified by HTs. In turn, fracture surfaces analysis reveals the relationship between microstructural changes and failure mechanisms. Results clearly show that silicon particles play a crucial role in determining the investigated properties, significantly influencing strength and conductivity. Moreover, despite being produced through recycling processes, the recycled alloy exhibits overall performance comparable to that of primary alloys. This confirms its potential for sustainable lightweight solutions without compromising properties
Preliminary Investigation on the Use of Recycled A356 Alloy for Semi-Solid Processing
No full textThe continuous demand for lightweighting vehicles leads to a significant increase in the use of aluminium alloys in the automotive sectors. The Al-Si-Mg aluminium alloys are widely applied in foundry processes to produce structural components, due to their high specific mechanical properties combined with good castability and corrosion resistance. Primary (from bauxite) alloys are often used to ensure the highest quality of such parts, nevertheless their production route causes high CO2 emissions. With the goal of reducing cradle-to-grave emissions of vehicles secondary (from recycling) Al-Si-Mg alloys are often used for cast products, however their percentage of impurities is considered too high for structural components. Lately, some Al-Si-Mg recycled alloys with a low content of Fe are available on the market as an alternative to primary alloys. Alongside the traditional foundry processes, semi-solid techniques are known to be able to increase the performance of Al-Si alloys. In this paper, a preliminary microstructural and mechanical characterization of secondary A356 alloys, manufactured by the ultrasound semi-solid method, was performed. In detail, both high Fe and low Fe recycled A356 alloys were investigated in comparison to the traditional primary one. The effect of the T6 heat treatment was also taken into account
The role of high recycled content and heat treatments on microstructure, mechanical properties, and sustainability for an AlSi10MnMg structural automotive component
Full text linkSecondary aluminum alloys are produced with end-of-life scraps and are gaining importance for environmental sustainability, thanks to their low intrinsic carbon footprint and energy saving compared to the primary ones. They are increasingly used in the automotive sector for large and complex cast components. However, recycled alloys contaminants like Fe promote the formation of brittle intermetallic compounds, which negatively affect tensile strength and ductility. This study compares the mechanical performance and environmental impact of primary and recycled high pressure die casting AlSi10MnMg (EN AB 43500) alloy under as-produced and heat-treated conditions. Samples were extracted from a die-cast automotive component and subjected to annealing and an optimized T6 heat treatment to balance strength and ductility. Microstructural analysis using field emission scanning electron microscopy revealed a similar pores area fraction, as well as shape, size, and distribution of brittle acicular β-Al5FeSi and polygonal α-Al15(Fe,Mn)3Si2 Fe-rich phases in the primary and recycled alloys under different heat treatment conditions. This similarity justifies the comparable mechanical behavior of the primary and recycled alloy, characterized by limited ductility in the as-produced condition, often insufficient for safety-critical structural components. Heat treatments significantly improved ductility, increasing it by 40–50 % after annealing and nearly doubling it after T6 due to the fragmentation, spheroidization, and coarsening of the eutectic Si. However, the microstructure change reduces strength by a third after annealing and by 20 % after T6, ultimately influencing the final fracture mechanisms. Moreover, heat treatments increase energy consumption, with annealing and T6 leading to about 25 % and 30 % rises, respectively, making them justified only for elongation enhancement
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
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