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Dataset supporting the thesis "Lightweight alloy design for laser-based additive manufacturing"
No full textThese data are related to the GA design of high entropy alloys, including the excel and MATLAB script.</span
Lightweight alloy design for laser-based additive manufacturing
No full textLightweight metals are key to reducing energy consumption and enhancing the performance of advanced structures in aerospace, automotive, and related industries. This thesis investigates three complementary strategies for developing high-performance lightweight alloys underpinned by laser-based processing and computational materials design.First, a novel laser welding-brazing approach was applied to an immiscible material system (Mg/steel), which traditionally suffers from weak metallurgical bonding. By developing thermodynamic models to guide the selection of intermediate elements, robust joints were achieved, thus enabling reliable multi-material structures. The obtained joint strength is the highest compared to all previously reported literature.Second, a composition-optimisation model based on precipitation growth kinetics was developed to design ultra-high-strength aluminium alloys for laser powder bed fusion (LPBF). Through direct post-processing (ageing), the as-printed alloys reached yield strengths up to 650 MPa—among the highest reported to date for printable Al alloys—by capitalising on a finely tuned nanoscale precipitate structure that suppresses hot cracking and refines grain morphology.Finally, a genetic algorithm-based framework was employed to design Ti-based high-entropy alloys (HEAs) featuring transformation-induced plasticity (TRIP) effects. This approach systematically integrated phase stability and manufacturability criteria to identify compositions with exceptional strength–ductility synergy, suitable for laser-based additive manufacturing.Overall, this thesis highlights how integrated computational–experimental strategies and advanced laser technologies can unlock unprecedented mechanical performance in lightweight alloys. The findings pave the way for next-generation structural materials, facilitating more efficient and sustainable engineering applications
High Entropy Alloy Strengthening Modelling
No full textHigh entropy alloys (HEAs) have recently drawn attention due to their excellent mechanical properties across wide temperature ranges. This is attributed to phase stability and a wide variety of strengthening mechanisms in operation. Solid solution, precipitation, dislocation, grain-boundary, twin-boundary and phase-transformation strengthening have been reported to play an important role in controlling their mechanical properties. With a focus on yield strength, this paper reviews the different hardening mechanisms reported in the literature. Mathematical formulations and key constant for describing each mechanism are presented and discussed. A strengthening mechanism modelling strategy for HEA design is outlined
Interfacial liquid control to realize superior comprehensive properties of microwelded NiTi-stainless steel joints for multifunctional biomedical device fabrication
No full textDissimilar joining of NiTi and stainless steel (SS) is important in biomedical applications but poses significant challenges due to brittle intermetallic compounds (IMCs) formation in the welds. Replacing harmful phases in fusion welding cannot fully eliminate brittle IMCs and may introduce toxic elements, while the mixing restriction in solid-state welding increases the process complexity and results in large plastic deformation that degrades NiTi functional properties. In this work, we present a novel methodology that achieves a solid-state joined interface in NiTi-SS fusion welding (i.e., resistance microwelding) through in-situ interfacial liquid control. By combining the advantages of both welding techniques, the current method produced NiTi-SS joints with superior strength, superelasticity and biocompatibility compared to NiTi joints or base metal. The ultrathin reaction layer at the solid-state joined interface contributedto a strong metallurgical bonding, while Joule heating effects and interfacial reactions enhanced superelasticity and biocompatibility of the joint. By demonstrating complete superelasticity on NiTi side, flexible deformation capacity on SS side, superior resistance to hydrogen embrittlement and electrochemical corrosion, and reduced Ni ion release and cytotoxicity, the welded joint shows great potential for the fabrication of multifunctional biomedical devices. Our work not only provides a comprehensive study ofNiTi-SS joining under the biomedical background, but also introduces a new strategy for controlling material interface and dissimilar-metal welding process
Design method of immiscible dissimilar welding (Mg/Fe) based on CALPHAD and thermodynamic modelling
No full textJoining dissimilar metals is a major challenge in joining technology; the weldability of immiscible systems is especially challenging. In this study, a design methodology for dissimilar welding is suggested. The Miedema model and Toop model are developed to calculate the thermodynamics of quaternary alloy systems (Mg-Fe-Al-Cu). Finite element modelling (FEM) of temperature fields and the calculation of phase diagrams (CALPHAD) are combined to provide prerequisite information for modelling. As a test subject, laser welded lap configuration joints of AZ31B magnesium alloy and DP590 steel with a copper coating were put into the design scheme. The interfacial elemental diffusion and formation of intermetallics (IMCs) along the interface during the welding process are predicted. This simulation design scheme predicts the interfacial reaction kinetics and identifies whether the intermediate element works or not. The effects of the Cu coating thickness on the weld constitution, interfacial microstructures and mechanical properties were studied. Cu coating promotes the weld formation fostering the metallurgical reaction of the fusion zone (FZ) with the steel brazing interface. The mechanism of interfacial reactions during the welding-brazing process has been clarified. The Vickers hardness distribution across the interface shows that the Cu-IMCs are ductile.</p
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
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