Microstructural stability of an Ni–Mo based Hastelloy after 10 MeV electron irradiation at high temperature
| Autor: | Dieter Isheim, David N. Seidman, Christian Abromeit, Nelia Wanderka, Alexander Bakai |
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| Rok vydání: | 2010 |
| Předmět: |
Materials science
Number density Alloy Metals and Alloys Analytical chemistry engineering.material Condensed Matter Physics Microstructure Fluence Crystallography Electron diffraction Transmission electron microscopy Materials Chemistry engineering Electron beam processing Irradiation Physical and Theoretical Chemistry |
| Zdroj: | International Journal of Materials Research. 101:631-636 |
| ISSN: | 2195-8556 1862-5282 |
| Popis: | The microstructural changes of a Hastelloy alloy under 10 MeV electron irradiation at 650 °C for 700 h to a total fluence of 2 × 10– 3 dpa (displacements per atom) were investigated by transmission electron microscopy and by 3-dimensional atom-probe tomography utilizing a local-electrode atom-probe tomograph. Transmission electron microscopy analysis before irradiation reveals two types of precipitates: (i) spheroidal with a mean diameter of 22 nm; and (ii) ones with an irregular morphology of a few nm in diameter. The spheroidal precipitates (i) are coherent with the fcc matrix and their number density is ∼3 × 1021 m– 3. Electron diffraction patterns from these precipitates exhibit superlattice reflections corresponding to the L12 ordered structure. The chemical composition as measured by atom-probe tomography, is about 75 at.% Ni with additions of Al, Ti and Mo. The other type of precipitate (ii) is mainly enriched in Ni and Mo and its number density is ca. 3.6 × 1022 m– 3. The diffuse diffraction intensity maxima arising from these precipitates are observed at fcc, which are attributed to compositional short-range order. After electron irradiation, the Ni – Al-rich precipitates (i) exhibiting L12 superlattice reflections have disappeared completely, while the diffuse intensity maxima from the Ni – Mo rich clusters (ii) are still visible. The results are discussed with respect to the influence of the electron irradiation on the morphology and structural changes of the ordered precipitates. |
| Databáze: | OpenAIRE |
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