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The systematic presence of the ternary phases U6Mo4Al43 and UMo2Al20 is reported in a U–Mo/Al interaction layer grown by thermal annealing. This work shows, therefore, the low Mo solubility in UAl3 and UAl4 binary phases; it contradicts the hypothesis of the formation of (U,Mo)Al3 and (U,Mo)Al4 solid solutions often admitted in the literature. Using µ‐XAS (micro X‐ray absorption spectroscopy) at the Mo K edge and µ‐XRD (micro X‐ray diffraction), the heterogeneity of the interaction layer obtained on a γ‐U0.85Mo0.15/Al diffusion couple has been precisely investigated. The UMo2Al20 phase has been identified at the closest location from the Al side. Moreover, µ‐XRD mapping performed on an annealed fuel plate enabled the characterization of the four phases resulting from the γ‐U0.85Mo0.15/Al and (U2Mo + α‐U)/Al interactions. A strong correlation between the concentrations of UAl4 and UMo2Al20 and those of UAl3 and U6Mo4Al43 has been shown.

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We have recently evidenced an original Raman signature of alpha irradiation-induced defects in UO 2. In this study, we aim to determine whether the same signature also exists in different actinide oxides, namely ThO 2 and PuO 2. Sintered UO 2 and ThO 2 were initially irradiated with 21 MeV He 2+ ions using a cyclotron device and were subjected to an in situ luminescence experiment followed by Raman analysis. In addition, a PuO 2 sample that has previously accumulated self-irradiation damage due to alpha particles was investigated only by Raman measurement. Results obtained for the initially white ThO 2 showed that a blue color appeared in the irradiated areas as well as luminescence signals during irradiation. However, Raman spectroscopic analysis showed the absence of Raman signature in ThO 2. In contrast, the irradiated UO 2 and PuO 2 confirmed the presence of the Raman signature but no luminescence peaks were observed. These findings lead to propose a mechanism involving electronic defects in ThO 2 while a coupling between electronic defects and phonons is needed to explain the Raman signal in UO 2 and PuO 2 .

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Pitting corrosion of a duplex stainless steel is studied under straining conditions. An original method based on successive X-ray diffraction measurements was first used both to quantify the surface stresses and to determine the elastoplastic behavior in the close vicinity of the surface of metallic phases. The time to pit was then measured under various levels of applied stress below the apparent yield strength by classical electrochemical tests under potentiostatic control. The evolution of the time to pit was then analyzed with respect to the individual elastoplastic behavior of phases. The results obtained indicate that the electrochemical behavior of duplex steels can be correlated to the surface stress state measured in the austenite phase.Numerous studies have been devoted to the influence of metallurgical ͑such as the presence of inclusions 1 and the content in alloying elements 2 ͒ and physicochemical ͑such as the temperature 3 and the nature of ions in solution 3,4 ͒ factors on pitting corrosion of stainless steels. By comparison, only a few studies have been concerned with the role of mechanical stresses in the corrosion susceptibility of these materials. When applying a high level of stress, irreversible changes are usually induced, corresponding to high levels of residual stress, emergence of slip bands, hardening, phase transformation, surface roughness, and microcracks. Laser peening, which produces plastic deformation and in turn compressive surface stresses, improves the stress corrosion cracking 5 and pitting 6 resistance of austenitic stainless steels. It has been demonstrated on austenitic alloys immersed in MgCl 2 at 117°C 5 that a cyclic prestraining at an applied strain amplitude of ⌬ p ϭ 10 Ϫ3 and a strain rate of 10 Ϫ3 s Ϫ1 up to a cumulative plastic strain of 20%, corresponding to the saturation regime in low-cycle fatigue, prior to stress corrosion cracking tests promotes the formation of low-energy dislocation structures with a two-dimensional cell structure which favors the relaxation of stress by dislocation emission from the cell walls. Thus, the formation of strong pileups is delayed and crack initiation resistance increases. By contrast, the deleterious effects of a monotonic prestraining at 5% strain 7 has been shown for both initiation and propagation of cracks ͑by inducing Lomer locks which enhance the formation of obstacles to dislocation motion and strong pileups͒. The effects of a plastic deformation on the corrosion rate of mild steel in H 2 SO 4 media was also examined and it was found both that the double-layer capacitance values increase with deformation as a result of an increase in surface roughness and that changes in the distribution and particle size of cementite introduced by deformation may accelerate corrosion by reducing the hydrogen overvoltage at cathodic sites. 8 Tensile residual stresses have deleterious effects on the corrosion behavior of metallic alloys 9 and the increase of the anodic current determined on 316 stainless steel from polarization curves at ...

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