High Temperature Scandium Containing Aluminum Alloys Subjected to Equal Channel Angular Pressing

Precipitation hardenable aluminum alloys are well-known for their high strengthto-weight ratio, good thermal stability, electrical conductivity, and low cost. Al-Sc alloys micro-alloyed with rare earth and transition metal elements can be strengthened for ambient and high temperature applications. This is primarily due to the precipitation of coherent, hard, finely distributed, and coarsening resistant, nanosized Al3(X) trialuminide precipitates. In addition to precipitation strengthening, equal channel angular pressing (ECAP) can be applied to further enhance mechanical properties of this system by microstructure modification. In this work, the effect of ECAP on microstructure modification, precipitate evolution, and mechanical response of a high temperature aluminum alloy with microadditions of Er, Sc, Zr, V, Si was investigated. Combined strengthening with yield strength up to ~180 MPa was achieved after aging to peak hardness followed by grain refinement through ambient temperature ECAP using route 4Bc. Subsequently, a different processing approach of ECAP after homogenization was also carried out. Tensile results showed only a slight improvement of about 2-5% in yield strengths of peak-aged followed by ECAP (PA-ECAP) alloy as compared to homogenized followed by ECAP (H-ECAP) alloy. Mechanical tests combined with calorimetry studies and scanning/transmission electron microscopy confirmed the occurrence of dynamic precipitation during ambient temperature ECAP of Al-Er-Sc-Zr-V-Si in homogenized condition. Hence, it was established that ECAP can significantly influence the kinetics and distribution of precipitates in these alloys. Furthermore, pre- and post- ECAPed alloys were subjected to annealing heat treatments. The variations in microhardness after annealing heat treatments at different temperatures highlighted the important role nanoprecipitates play in maintaining microstructure stability of Al-Er-Sc-Zr-V-Si before and after ECAP. Microstructure evolution during static annealing (without the application of load) and dynamic annealing (with applied load) was also studied using interrupted high temperature tensile tests followed by electron backscatter diffraction (EBSD) analysis. Results showed that there is a difference in deformation mechanism for H-ECAP and PA-ECAP. Among the two processing routes, although the magnitude of static and dynamic grain growth in H-ECAP condition was found to be higher than PA-ECAP condition, it showed superior elevated temperature strength and ductility. Lastly, electrochemical characteristics of Al-Er-Sc-Zr-Si with micro-additions of Group 5 transition elements (V, Nb, or Ta) added individually and then exposed to saline media. There is slight increase in activity of Al-Er-Sc-Zr-Si after addition of any of Group 5 elements (V, Nb, or Ta) which justifies their addition to improve ambient and elevated temperature mechanical properties. The order of mechanical strength is Al-Er-Sc-Zr-Si-V > Al-Er-Sc-Zr-Si-Nb > Al-Er-Sc-Zr-Si-Ta > Al-Er-Sc-Zr-Si

An empirical study of vulnerabilities in edge frameworks to support security testing improvement

peer reviewedEdge computing is a distributed computing paradigm aiming at ensuring low latency in modern data intensive applications (e.g., video streaming and IoT). It consists of deploying computation and storage nodes close to the end-users. Unfortunately, being distributed and close to end-users, Edge systems have a wider attack surface (e.g., they may be physically reachable) and are more complex to update than other types of systems (e.g., Cloud systems) thus requiring thorough security testing activities, possibly tailored to be cost-effective. To support the development of effective and automated Edge security testing solutions, we conducted an empirical study of vulnerabilities affecting Edge frameworks. The study is driven by eight research questions that aim to determine what test triggers, test harnesses, test oracles, and input types should be considered when defining new security testing approaches dedicated to Edge systems. preconditions and inputs leading to a successful exploit, the security properties being violated, the most frequent vulnerability types, the software behaviours and developer mistakes associated to these vulnerabilities, and the severity of Edge vulnerabilities. We have inspected 147 vulnerabilities of four popular Edge frameworks. Our findings indicate that vulnerabilities slip through the testing process because of the complexity of the Edge features. Indeed, they can’t be exhaustively tested in-house because of the large number of combinations of inputs, outputs, and interfaces to be tested. Since we observed that most of the vulnerabilities do not affect the system integrity and, further, only one action (e.g., requesting a URL) is sufficient to exploit a vulnerabilityR-AGR-3929 - IPBG19/14016225/INSTRUCT - SES (01/10/2020 - 30/09/2026) - CHATZINOTAS Symeo

Structure and Growth of Core–shell Nanoprecipitates in Al–Er–Sc–Zr–V–Si High-temperature Alloys

Lightweight Sc-containing aluminum alloys exhibit superior mechanical performance at high temperatures due to core–shell, L12-ordered trialuminide nanoprecipitates. In this study, the structure of these nanoprecipitates was studied, using different transmission electron microscopy (TEM) techniques, for an Al–Er– Sc–Zr–V–Si alloy that was subjected to a two-stage overaging heat treatment. Energy-dispersive X-ray spectroscopy of the spherical Al3(Sc, Zr, Er ,V) nanoprecipitates revealed a core–shell structure with an Sc- and Er-enriched core and a Zr-enriched shell, without a clear V outer shell. This structure is stable up to 72% of the absolute melting temperature of Al for extended periods of time. High-angle annular dark-field scanning TEM was used to image the {100} planes of the nanoprecipitates, demonstrating a homogeneous L12-ordered superlattice structure for the entire nanoprecipitates, despite the variations in the concentrations of solute atoms within the unit cells. A possible growth path and compositional trajectory for these nanoprecipitates was proposed using high-resolution TEM observations, where different rod-like structural defects were detected, which are considered to be precursors to the spherical L12-ordered nanoprecipitates. It is also hypothesized that the structural defects could consist of segregated Si; however, this was not possible to verify with HAADF-STEM because of the small differences in Al and Si atomic numbers. The results herein allow a better understanding of how the Al–Sc alloys’ core–shell nanoprecipitates form and evolve temporally, thereby providing a better physical picture for future atomistic structural mappings and simulations

National guidelines for the diagnosis and treatment of hilar cholangiocarcinoma

©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.Peer reviewe

Replication Package for manuscript entitled "Field-based Security Testing of SDN configuration Updates" by Jahanzaib MALIK and Fabrizio PASTORE

<p><span><span>This is the replication package for the paper titled “<em>Field-based Security Testing of SDN configuration Updates</em>” authored by Jahanzaib MALIK and Fabrizio PASTORE.</span></span></p&gt

High Temperature Scandium Containing Aluminum Alloys Subjected to Equal Channel Angular Pressing

Precipitation hardenable aluminum alloys are well-known for their high strengthto-weight ratio, good thermal stability, electrical conductivity, and low cost. Al-Sc alloys micro-alloyed with rare earth and transition metal elements can be strengthened for ambient and high temperature applications. This is primarily due to the precipitation of coherent, hard, finely distributed, and coarsening resistant, nanosized Al3(X) trialuminide precipitates. In addition to precipitation strengthening, equal channel angular pressing (ECAP) can be applied to further enhance mechanical properties of this system by microstructure modification. In this work, the effect of ECAP on microstructure modification, precipitate evolution, and mechanical response of a high temperature aluminum alloy with microadditions of Er, Sc, Zr, V, Si was investigated. Combined strengthening with yield strength up to ~180 MPa was achieved after aging to peak hardness followed by grain refinement through ambient temperature ECAP using route 4Bc. Subsequently, a different processing approach of ECAP after homogenization was also carried out. Tensile results showed only a slight improvement of about 2-5% in yield strengths of peak-aged followed by ECAP (PA-ECAP) alloy as compared to homogenized followed by ECAP (H-ECAP) alloy. Mechanical tests combined with calorimetry studies and scanning/transmission electron microscopy confirmed the occurrence of dynamic precipitation during ambient temperature ECAP of Al-Er-Sc-Zr-V-Si in homogenized condition. Hence, it was established that ECAP can significantly influence the kinetics and distribution of precipitates in these alloys. Furthermore, pre- and post- ECAPed alloys were subjected to annealing heat treatments. The variations in microhardness after annealing heat treatments at different temperatures highlighted the important role nanoprecipitates play in maintaining microstructure stability of Al-Er-Sc-Zr-V-Si before and after ECAP. Microstructure evolution during static annealing (without the application of load) and dynamic annealing (with applied load) was also studied using interrupted high temperature tensile tests followed by electron backscatter diffraction (EBSD) analysis. Results showed that there is a difference in deformation mechanism for H-ECAP and PA-ECAP. Among the two processing routes, although the magnitude of static and dynamic grain growth in H-ECAP condition was found to be higher than PA-ECAP condition, it showed superior elevated temperature strength and ductility. Lastly, electrochemical characteristics of Al-Er-Sc-Zr-Si with micro-additions of Group 5 transition elements (V, Nb, or Ta) added individually and then exposed to saline media. There is slight increase in activity of Al-Er-Sc-Zr-Si after addition of any of Group 5 elements (V, Nb, or Ta) which justifies their addition to improve ambient and elevated temperature mechanical properties. The order of mechanical strength is Al-Er-Sc-Zr-Si-V > Al-Er-Sc-Zr-Si-Nb > Al-Er-Sc-Zr-Si-Ta > Al-Er-Sc-Zr-Si