Fast in-situ annealing stage coupled with EBSD: A suitable tool to observe quick recrystallization mechanisms

International audienceA heating stage has been developed to perform in-situ annealing in a SEM equipped with an EBSD system in order to study recrystallization mechanisms. High temperature treatments could then be performed inside the SEM, up to 1180 °C and with high heating and cooling rates (~ 100 °C s− 1). Samples were cooled down to room temperature to perform EBSD orientation mapping in between successive short-duration heat treatments. Microstructure evolution snapshots obtained this way allow gaining an insight into recrystallization mechanisms. The interest of such experiments is shown for two examples: static recrystallization of cold deformed pure tantalum and post‐dynamic evolution of hot-deformed Zircaloy4

EBSD coupled to SEM in situ annealing for assessing recrystallization and grain growth mechanisms in pure tantalum

International audienceAn in situ annealing stage has been developed in-house and integrated in the chamber of a Scanning Electron Microscope equipped with an Electron BackScattered Diffraction system. Based on the Joule effect, this device can reach the temperature of 1200°C at heating rates up to 100°C/s, avoiding microstructural evolutions during heating. A high-purity tantalum deformed sample has been annealed at variable temperature in the range 750°C-1030°C, and classical mechanisms of microstructural evolutions such as recrystallization and grain coarsening phenomena have been observed. Quantitative measurements of grain growth rates provide an estimate of the mean grain boundary mobility, which is consistent with the value estimated from physical parameters reported for that material. In situ annealing therefore appears to be suited for complementing bulk measurements at relatively high temperatures, in the context of recrystallization and grain growth in such a single-phase material

Mesures des hétérogénéités de déformation du tantale déformé à froid et conséquences sur la recristallisation

National audienceLa recristallisation statique du tantale est fortement dépendante de la microstructure engendrée lors de la mise en forme. Des échantillons présentant de faibles taux de déformation ont été obtenus par des essais mécaniques simples de torsion et de compression. Leur observation par microscopie électronique à balayage ainsi que la réalisation de cartographies d'orientation par EBSD, associées à des traitements thermiques in situ, ont permis de montrer qu'un grain avec un facteur de Taylor élevé recristallisait plus vite. Par ailleurs, une méthode « globale » d'évaluation de la densité de dislocations à partir de mesures de dureté a été mise en place. Elle permet d'estimer l'énergie stockée par le matériau lors de sa déformation, énergie qui peut ensuite être reliée au déclenchement de la recristallisation. Cette approche est particulièrement intéressante pour des échantillons déformés sévèrement suivant un chemin de déformation complexe, pour lesquels le calcul des facteurs de Taylor à partir d'une microstructure déformée revêt moins de sens

Familles et migrations France, 1962-2013 vingt-et-un récits de vie

résultats d'une enquête menée par 21 étudiant-e-s de Lyon auprès de 21 migrants arrivé-e-s en France et principalement dans la région lyonnaise entre 1963 et 201

Quasi In situ EBSD investigation of static recrystallization in 304L stainless steel at elevated temperature

The microstructural evolution of deformed 304L stainless steel during static recrystallization and grain growth was characterized by EBSD within an SEM chamber, which enabled microstructural and crystallographic information to be determined. The experimental procedures are discussed. The sample was heated at constant temperature for a short time (a few seconds), followed by an intermediate cooling in order to perform scans. This cycle was repeated on the same sample to capture a slowly recrystallizing microstructure. The important aspects in static recrystallization process including nuclei location, nucleation rate and grain growth are all discussed. Special attention is paid on grain boundary migration velocity at high temperature up to 1000°C by investigation of the character of slow and fast moving interfaces

Engraved horse incisors during the Middle Magdalenian (France)

International audienceEngraved horse incisors during the Middle Magdalenian (France

Engraved horse incisors during the Middle Magdalenian (France)

Engraved horse incisors during the Middle Magdalenian (France

Critical recrystallization during sub-solvus annealing in a polycrystalline Nickel- based superalloy

International audienceSelective and exaggerated growth of some grains is a phenomenon which is likely to occur during annealing following forging operations, in Nickel-based superalloys. It has been investigated in the Rene 65 alloy in terms of metallurgical characteristics of such grains, mechanisms and kinetics. The nature of this phenomenon, which is commonly reported as abnormal grain growth, is discussed based on the obtained results and appears to be a case of critical recrystallization

EBSD coupled to SEM in-situ annealing as a tool to identify recrystallization mechanisms - Application to Zr and Ta alloys

International audienceA heating stage as been developed to perform in-situ annealing in a SEM equipped with an EBSD system in order to study recrystallization mechanisms. High temperature treatments could then be performed inside the SEM, up to 1180°C and with high heating- and cooling-rates (∼100°C.s -1). Samples were cooled down to room temperature to perform EBSD orientation mapping in between successive short-duration heat-treatments. Microstructure evolution snapshots obtained this way are presented in this paper to show recrystallization in Zircaloy4 and in pure tantalum

Development of overgrown grains during sub-solvus heat treatment in a polycrystalline γ-γ’ Nickel-based superalloy

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