, Déformation intra vs intergranulaire : effet de la température sur la déformation hors

. .. À-haute-température,

.. .. Bilan,

, Vers une meilleure résolution : analyse avec une microgrille ayant un pas de 1 µm

.. .. Simulations,

. .. Perspectives-techniques, , p.262

. .. Vers-de-nouveaux-champs-de-recherche, , p.262

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, Dans cette annexe on va détailler à la fois le principe de fonctionnement des MEB FEG et plus particulièrement du MEB Gemini SEM 500 de chez ZEISS

, Ce canon à effet de champs est constitué d'une cathode Schottky sous forme d'une pointe en tungstène avec un réservoir de ZrO, d'un suppresseur, d'une anode extractrice et d'une d'anode accélératrice. L'anode extractrice permet d'extraire les électrons de la pointe, tandis que l'anode accélératrice va quant à elle fournir la tension d'accélération des électrons. Le faisceau va ensuite passer à l'intérieur d'un condenseur afin d'arriver à un booster. Le booster va permettre d'accélérer le faisceau (+8 kV) jusqu'à la lentille finale, A.1 MEB Pour un MEB FEG (Field Emission Gun), le faisceau d'électrons est émis à l'aide d'un canon à effet de champs

M. Le and . Gemini, Pour une tension de 15 kV, la résolution du MEB Gemini SEM 500 est égale à 0,5 nm. La technologie du booster et la lentille "Nano-twin" donnent l'opportunité d'améliorer la collecte d'électrons secondaires (SE) même pour de grande distance de travail. À la sortie de la lentille objective, le faisceau est focalisé en un point sur l'échantillon. Lors du balayage du faisceau sur l'échantillon, il y a une interaction électrons/matière. Suite à cette interaction avec les électrons incidents, il y a la formation d'une poire d'interaction. À la suite de cette interaction, l'échantillon émet certaines particules sous forme d'électrons ou de rayonnement X comme le schématise la Figure A.1 (a). Les particules émises proviennent de différentes profondeurs de l'échantillon, et sont donc différentes selon cette profondeur comme le montre la Figure A.1 (b), SEM 500 possède également une lentille appelée "Nano-twin". Cette lentille combine un champ magnétique et électrostatique, cela permet ainsi de maximiser les performances d'observation pour des observations à très faible tension (1 kV), de travailler à très haute résolution (0,9nm) tout en réduisant les aberrations sphériques et chromatiques [Maniguet, 2015.

, (a) montre un point non indexé (pixel blanc), après un nettoyage par "Grain Dilatation" le point est indexé comme l'illustre la Figure C.2 (b). Pour passer de la Figure C.2 (a) à la Figure C.2 (b), le logiciel regarde l'orientation des points indexés qui sont voisins du point non indexé. Puis il détermine la meilleure correspondance possible afin de considérer ce point comme l'un des voisins l'entourant. Les conditions de, La Figure C, vol.2

, Ici lorsque l'on regarde la Figure C.3 (b), un grain est défini selon une couleur. Chaque couleur correspond à une orientation cristallographique, cela signifie que si un grain est de couleur rouge alors il a une orientation définie selon le plan {0001}. Avec le "Grain Dilatation" on vient indexer les points qui initialement ne le sont pas. La Figure C.3 (d) montre un nettoyage par, -nombre minimum du pixel qui composent un grain = 50, On répète cette itération cinq fois par carte en veillant à ne pas supprimer ou introduire des informations microstructurales