Investigations of the microstructure and mechanical properties of prior-β structure as a function of the oxygen content in two zirconium alloys
| Autor: | Anthony Stern, Jean-Christophe Brachet, Valérie Maillot, Didier Hamon, Françoise Barcelo, Sylvie Poissonnet, André Pineau, Jean-Paul Mardon, Anne Lesbros, M. Limback, B. Kammenzind, S. W. Dean |
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| Přispěvatelé: | Service des Recherches Métallurgiques Appliquées (SRMA), Département des Matériaux pour le Nucléaire (DMN), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Centre des Matériaux (MAT), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), AREVA NP, AREVA NP - Centre Technique (FRANCE), Direction Technique (EDF Direction Technique), EDF (EDF), Centre des Matériaux (CDM), Mines Paris - PSL (École nationale supérieure des mines de Paris) |
| Jazyk: | angličtina |
| Rok vydání: | 2008 |
| Předmět: |
Environmental Engineering
Materials science phase transformation zirconium alloys post-quench ductility Oxide chemistry.chemical_element 02 engineering and technology element partitioning 01 natural sciences Oxygen [SPI.MAT]Engineering Sciences [physics]/Materials chemistry.chemical_compound low-tin Zircaloy-4 0103 physical sciences Ultimate tensile strength General Materials Science M5® Composite material Phase diagram LOCA 010302 applied physics Metallurgy Zirconium alloy Public Health Environmental and Occupational Health General Engineering 021001 nanoscience & nanotechnology Microstructure high temperature oxidation Nuclear Energy and Engineering chemistry Limiting oxygen concentration multilayered samples 0210 nano-technology Electron backscatter diffraction |
| Zdroj: | Journal of ASTM International (JAI) Journal of ASTM International (JAI), ASTM, 2008, 5, pp.71-90. ⟨10.1520/JAI101119⟩ Journal of ASTM International (JAI), 2008, 5, pp.71-90. ⟨10.1520/JAI101119⟩ |
| ISSN: | 1546-962X |
| DOI: | 10.1520/JAI101119⟩ |
| Popis: | International audience; It is now well acknowledged that, after a prototypical loss of coolant accident (LOCA) transient, the resultant mechanical properties of fuel cladding tubes depend strongly on the oxygen content of the residual prior-β layer, as this phase is the only metallic part of the high-temperature oxidized cladding that may show some residual ductility. The aim of this study is to obtain relevant information on the evolution of the mechanical properties, on the one hand, of the prior-β structure as a function of the oxygen content, assuming that there is a critical oxygen content that leads to a ductile-to-brittle failure mode transition at low testing temperatures (20–135°C); and on the other hand, of the α(O) structure as a function of the oxygen content. Sheets of Zircaloy-4, 1 to 3 mm thick, and M5® advanced alloys from AREVA NP have been studied. To obtain different oxygen contents, they were oxidized at high temperature and then annealed under vacuum in order to reduce the oxide layer. Systematic post-treatment measurements of the oxygen concentration and of its homogeneity within the sheet thickness were performed. The different prior-β and α(O) structures thus obtained have homogeneous oxygen content between ∼0.14 wt. % and 0.9 wt. % and ∼2 wt. % and 7 wt. %, respectively. Such oxygen concentration ranges cover the solubility values that are expected in the β phase and in the α(O) phase at high temperatures typical of LOCA transients. Detailed microstructure investigations were subsequently performed on the prior-β structures since it is considered to be the most important layer when regarding the post-quench mechanical behavior of the material. Continuous cooling temperature (CCT) phase diagrams as a function of the oxygen content were established to correctly interpret the results. Electron backscattered diffraction (EBSD) analysis has then allowed the crystallographic orientations and the morphology of prior-β phase sub-grains to be determined. For each considered prior-β grain, it was possible to interpret the data by taking into account the “Bürgers” crystallographic relationship between the parent β phase and the resultant α phase. Complementary electron probe microanalysis (EPMA) was also used. These last experiments have shown a spatial fluctuation of the oxygen content within the microstructure that depends both on the nominal oxygen content and on the cooling rate. Nanohardness measurements were also performed and correlated with this oxygen spatial partition. These measurements proved to be useful for the understanding of the tensile macroscopic mechanical behavior. Finally, on the one hand, tensile tests were performed on prior-β phase at testing temperatures ranging from −100°C up to 260°C. The ductile-to-brittle temperature transition and the mechanical constitutive laws as a function of the oxygen content were then described. These tests show the existence of a ductile-to-brittle failure mode transition at 20°C for a critical oxygen concentration of ∼0.5 wt. %. A detailed fractographic analysis was performed to assess the failure mechanism. On the other hand, four-point bending tests were conducted on α(O) phase at 25°C and 135°C in order to obtain behavior laws. Preliminary finite element calculations were performed to simulate ring compression tests carried out on multi-layered high-temperature oxidized cladding tubes. |
| Databáze: | OpenAIRE |
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