Marmy, P.

Möslang, A.

Vladimirov, P.V.

English

Vladimirov, P. V.

KITopen

1Forschungszentrum Karlsruhe GmbH, Institut für Materialforschung-I, Postfach 36 40, 76021 Karlsruhe2Fusion Technology Materials, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, CH-5232, Villigen-PSI, SwitzerlandP. Vladimirov1, A. Möslang1, P. Marmy2mit der Universität Karlsruhe verbunden inNUCLEAR RESPONSES IN IFMIF CREEP-FATIGUE TESTING MACHINEHow ODS particles are formed?Oxide dispersion strengthened (ODS) steels are produced by mechanical alloying followed by powder consolidation (e.g., hot isostatic pressing≡hipping) at temperature around 1000-1200°C and pressure ~100 MPa.Contemporary view: Oxide particles found after hipping are the remnants of the initial oxide powder crushed by mechanical alloying (MA) incorporated into steel matrix. This view is supported by the fact that the hipping temperature is much lower than the melting temperature of yttria (Tm ~2410°C) and therefore any thermal processes of oxide particle transformation should be excluded. New insight:Experiments performed by other groups on 12-14%Cr ferritic steels have shown:• SAXS, SANS and TEM analysis of MA powder show no traces of yttria particles • SANS shows formation of nanoclusters (NCs) after annealing of MA powder at temperatures higher than 850°C. The NC sizes increase and their volume fractions and number densities decrease with increasing the consolidation temperature in the manner consistent with Ostwald ripening process.• ODS particles are stable during annealing at hipping temperature for a long time (e.g.,    243 h @ 1150°C)• Addition of Ti could hardly affect MA process, however, resulting in formation of smaller ODS particles• Addition of Ti in the form of oxides results in formation of mixed Y-Ti oxides• 3D atomic probe performed on hipped ODS ferritic steels reveals:• presence of Y and O in solid solution• significant (x16 times) increase of Y concentration near dislocations• formation of nm-sized spherical zones with increased concentration of Y and O.The experiments performed on 9%Cr ferritic-martensitic ODS steels (Eurofer) presented in this work are consistent with the results obtained by other groups for 14%Cr ferritic steels.Results: 3D Atomic Probe Analyses of Eurofer ODSMaterials: Eurofer and Eurofer ODS (0.5%Y2O3) Samples preparation: cutting performed by electro-chemical erosion methodMethod: Energy Compensated Optical Tomography Atomic Probe (ECOTAP).      Cu S V O Y      Cu S V O Y  Results: ODS-Ferrite Matrix Orientation RelationshipMaterial: Eurofer ODS (0.5% Y2O3) hipped and temperedKurdjumov-Sachs type orientation relationship was observed:〈111〉M || 〈110〉P  and 〈-110〉M || 〈-111〉PODS particles are partly coherent with ferrite matrix.(011)(222)(222)(222)(222)(011)(101)(101)(110)(110)b)〈11-2〉M ||〈11-2〉P〈111〉M || 〈110〉P〈-110〉M || 〈-111〉 P〈111〉M ||〈110〉P〈-1-12〉M || 〈-1-12〉P〈-110〉M || 〈-111〉P• as MA2h@1100°CMaterial ECOTAP results Eurofer No impurity segregations  Eurofer ODS Two types of zones with increased impurity concentrations were found: • Spherical zones of  ~3x3x3 nm3 • Plate-like zones with thickness of ~2 nm, spacing between layers varies from 2 to 30 nm within the same sample  Results: SANS on MA Eurofer ODS PowderConclusionsbased on the results for ferritic and ferritic-martensitic ODS steels:• Yttrium oxide particles added to steel powder are destroyed and, at least, partly dissolved in the matrix during MA.• ODS particles form during hipping (or during cooling after hipping) by precipitation of dissolved atoms • Once formed ODS particles are stable and coarsen only at temperatures higher that the hipping one.• Small spherical zones found by 3D atomic probe can be considered as precursor of precipitates.• Addition of Ti, which compete with Y for O, changes the kinetics of precipitation resulting in formation of smaller particles.a)HRTEM micrograph of Y2O3 particle embedded into ferrite matrix (a) and its Fourier transformation as well as crystallographic model showing yttrium and iron atom positions corresponding to the observed orientation relationship (c).c)Production step SANS results powder as MA  no NCs observed MA powder annealed at 1100°C for 2 h NCs of ~ 10 nm  Material: 9%Cr EUROFER ODS (0.5% Y2O3) powder300 nmResults: TEM of Eurofer SamplesR. Schaeublin et al., JNM 307-311 (2002) 778-782

Material responses in IFMIF creep-fatigue testing machine

https://publikationen.bibliothek.kit.edu/220069335/3815059

Material responses in IFMIF creep-fatigue testing machine

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