Study of the Oxidation Assisted Intergranular Cracking Mechanism on a Ni-Base Superalloy

In order to collect accurate information about the widely reported Oxidation Assisted Intergranular Cracking (OAIC) mechanism of the superalloy 718 at 650 °C in air environment, we investigated a new tensile test procedure which enables to have access to a quantitative semi-continuous assessment of the damaging process of the alloy 718 during a standard tensile test. Tensile tests were carried out on a solutionized and aged alloy 718 by varying the deformation mode of the alloy during the ongoing experiment. The semi-continuous quantification of the intergranular damage was performed after a fracture surface analysis of samples tested in both Dynamic Strain Ageing (DSA) domain and DSA-subdomain where Portevin-Le Chatelier (PLC) effect occurs. This innovative testing method allows to characterize the intergranular damage that occurs when the material is stressed with an unserrated DSA deformation mode as the alloy 718 is only sensitive to OAIC in this domain. In these conditions, the onset of the intergranular cracking process was found to be around 10% of total strain. An increase in the cracking kinetic when necking occurs was also noticed. A close connection between the intensity of the intergranular damage and the cumulated strain in DSA deformation mode before the onset of the damaging process was found. The gathered information represents a significant improvement in the understanding of still debated OAIC or Stress Corrosion Cracking (SCC) mechanisms

Temperature-dependance evalutation on deformation processes in the Alloy 718 using high-resolution digital image correlation

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The SIB Swiss Institute of Bioinformatics' resources: focus on curated databases

The SIB Swiss Institute of Bioinformatics (www.isb-sib.ch) provides world-class bioinformatics databases, software tools, services and training to the international life science community in academia and industry. These solutions allow life scientists to turn the exponentially growing amount of data into knowledge. Here, we provide an overview of SIB's resources and competence areas, with a strong focus on curated databases and SIB's most popular and widely used resources. In particular, SIB's Bioinformatics resource portal ExPASy features over 150 resources, including UniProtKB/Swiss-Prot, ENZYME, PROSITE, neXtProt, STRING, UniCarbKB, SugarBindDB, SwissRegulon, EPD, arrayMap, Bgee, SWISS-MODEL Repository, OMA, OrthoDB and other databases, which are briefly described in this article

Oxidation assisted intergranular cracking and stress corrosion cracking of thin products made of alloy 718 : effect of microstructure and grain boundary composition

Du fait de ses bonnes caractéristiques générales, l’alliage 718 est utilisé pour la fabrication de certains composants présents dans les assemblages combustibles des Réacteurs à Eau Pressurisée (REP). Malgré la relative résistance à l’amorçage de défauts de Corrosion Sous Contrainte (CSC) de cet alliage, l’amélioration recherchée de la fiabilité et de la sureté des installations nucléaires nécessite une compréhension approfondie de ce mécanisme d’endommagement et la mise en place de solutions industrielles visant à augmenter les marges de fonctionnement de ces composants. Ainsi, une modification de la gamme de fabrication est envisagée par Framatome afin d’accroitre la résistance à la CSC des composants en alliage 718. L’identification des effets de l’état métallurgique est essentielle afin d’appréhender le mécanisme de CSC et d’appuyer la solution industrielle retenue. Sur ce point, les effets de la précipitation de la phase et de l’écrouissage sur la sensibilité à la fissuration intergranulaire du matériau ont été étudiés et l’identification des mécanismes de déformation mis en jeu aux joints de grains entreprise. La précipitation de la phase et l’écrouissage se révèlent être bénéfiques et améliorent la résistance à l’amorçage de fissures intergranulaires de l’alliage 718. Néanmoins, il a été montré qu’ils ne permettaient pas la désensibilisation totale du matériau à eux seuls. En outre, une composante de déformation par glissement intergranulaire a été identifiée dans le cas de coulées d’alliage 718 sensibles à la fissuration intergranulaire, et est partiellement inhibée pour le matériau issu de la gamme de fabrication modifiée. Ces observations ont abouti à la proposition d’un mécanisme d’amorçage basé sur ce mode de déformation particulier. Les différents résultats obtenus constituent un apport considérable quant à la compréhension du mécanisme de CSC de l’alliage 718. Ils amènent également des éléments d’explication du bon comportement du matériau issu de la gamme de fabrication modifiée. Aussi les résultats d’essais visant à éprouver la résistance à l’endommagement du nouveau matériau, montrent toute la pertinence de la solution industrielle envisagée face à la problématique rencontréeDue to its good resistance to Stress Corrosion Cracking (SCC), some of the components of nuclear assemblies of Pressurized Water Reactors (PWR) are made of alloy 718. Nevertheless, the current trend is increasing the liability and the safety of nuclear plants and needs a further understanding of the SCC mechanism of the material. Framatome is also considering a modification of the processing route of the strips used for the manufacturing of these components in order to improve the SCC resistance of the alloy 718. To better understand the SCC mechanism and support the solution undertaken, the influence of the metallurgical state on the damaging process must be investigated. The influences of the precipitation of phase and cold working on the susceptibility to intergranular cracking of the alloy were examined and the deformation mechanism at grain boundaries identified. It was shown that these two features were beneficial and improve the cracking resistance of the alloy but could not provide full desensitization when taken separately. Furthermore, grain boundary sliding was identified on the material susceptible to SCC whereas it is partially suppressed on the resistant one. From these observations, a mechanism for the initiation of intergranular cracks based on grain boundary sliding has been proposed. This work is a valuable contribution for the better understanding of the SCC mechanism of the alloy 718 and provides an explanation to the higher cracking resistance of the material derived from the new processing route. In addition, the relevance of the industrial solution to suit the problematic encountered was put forwar

Strain localization in the Alloy 718 Ni-based superalloy: From room temperature to 650 °C

International audienceIrreversible deformation in relation to the microstructure was investigated for a polycrystalline Ni-based superalloy (Alloy 718) from room temperature to 650 °C using high-resolution digital image correlation (HR-DIC) techniques. Interrupted tensile tests were performed under a protective atmosphere to ensure the stability of the speckle pattern to track kinematics fields from surface analyses. In-plane strain localization was captured using HR-DIC on scanning electron microscopy (SEM) images. A statistical analysis of different strain localization events in relation to the microstructural features was conducted, i.e., intragranular slip localization, slip localization parallel to and near Σ3-twin boundaries (Σ3-TB), and grain boundary sliding (GBS). Alloy 718 exhibited slip localization at room temperature and 350 °C. Intense strain localization develops parallel and in the vicinity of Σ3-TB from the onset of the microplasticity. Few intense slip stimulated-grain boundary sliding events were found due to slip localization on both grains adjacent to the grain boundary. At 650 °C, Alloy 718 experienced grain boundary sliding at the onset of the yield without particular slip localization in adjacent grains. At lower temperatures, strain localization parallel to and near Σ3-TB was intense, and intragranular slip localization intensified with increasing macroscopic deformation. Particular microstructural configurations were found at 650 °C leading to premature damage: (i) sub-surface cavitation at grain boundaries, and (ii) grain boundary cracking due to intense shearing near a Σ3-TB

Pomp\ue9i. Villa de Diom\ue8de. Campagne d\u2019\ue9tude 2015

L\u2019objectif de la troisi\ue8me campagne men\ue9e sur la Villa de Diom\ue8de \ue9tait de pr\ue9ciser la chronologie relative du b\ue2timent et son \ue9volution en fonction des rapports de propri\ue9t\ue9 et d\u2019occupation de l\u2019espace qui organisent ce secteur p\ue9riurbain de Pomp\ue9i. Dans l\u2019angle sud-est de la villa, un secteur particuli\ue8rement propice pour l\u2019\ue9tude a \ue9t\ue9 privil\ue9gi\ue9, afin de caract\ue9riser la relation avec la Via delle Tombe, ainsi qu\u2019avec les fa\ue7ades orientale et m\ue9ridionale, dans la continuit\ue9 de l\u2019\ue9tude entreprise en 201

From bag-of-genes to bag-of-genomes: metabolic modelling of communities in the era of metagenome-assembled genomes

International audienc

Critical Assessment of Metagenome Interpretation: the second round of challenges.

Evaluating metagenomic software is key for optimizing metagenome interpretation and focus of the Initiative for the Critical Assessment of Metagenome Interpretation (CAMI). The CAMI II challenge engaged the community to assess methods on realistic and complex datasets with long- and short-read sequences, created computationally from around 1,700 new and known genomes, as well as 600 new plasmids and viruses. Here we analyze 5,002 results by 76 program versions. Substantial improvements were seen in assembly, some due to long-read data. Related strains still were challenging for assembly and genome recovery through binning, as was assembly quality for the latter. Profilers markedly matured, with taxon profilers and binners excelling at higher bacterial ranks, but underperforming for viruses and Archaea. Clinical pathogen detection results revealed a need to improve reproducibility. Runtime and memory usage analyses identified efficient programs, including top performers with other metrics. The results identify challenges and guide researchers in selecting methods for analyses