The effect of severe plastic deformation on the deuterium retention in tungsten exposed to high-flux low-energy plasma (flux ∼ 1024 D/m2/s, energy ∼ 50 eV, and fluence up to 3 × 1026 D/m2) at the plasma generator Pilot-PSI was studied by thermal desorption spectroscopy and scanning electron microscopy. The desorption spectra in both reference and plastically deformed samples were deconvolved into three contributions attributed to the detrapping from dislocations, deuterium-vacancy clusters, and pores, respectively. The plastically induced deformation, resulting in high dislocation density, does not change the positions of the three peaks, but alters their amplitudes as compared to the reference material. The appearance of blisters detected by scanning electron microscopy and the desorption peak attributed to the release from pores (i.e., deuterium bubbles) were suppressed in the plastically deformed samples but only up to a certain fluence. Beyond 5 × 1025 D/m2, the release from the bubbles in the deformed material is essentially higher than in the reference material. Based on the presented results, we suggest that a dense dislocation network increases the incubation dose needed for the appearance of blisters, associated with deuterium bubbles, by offering numerous nucleation sites for deuterium clusters eventually transforming into deuterium-vacancy clusters by punching out jogs on dislocation lines.

Defect properties of neutron irradiated Fe-Cr-C alloys and their influence on the mechanical behavior are studied by combining mechanical tests, microstructural examination, and the results of models. It is found that the initial microstructure of these alloys, determined by the Cr and C concentrations, as well as by the thermal treatment, can account for different defect formation and distribution after neutron irradiation. On the basis of these results, a correlation between defect properties and macroscopic mechanical behavior is proposed.

Taking the example of tungsten, we demonstrate that high-flux plasma exposure of recrystallized and plastically deformed samples leads to principal differences in the gas trapping and associated surface modification. Surface of the exposed predeformed samples exhibits ruptured µm-sized blisters, a signature of bubbles nucleated close to the surface on the plastically induced dislocation network. Contrary to the recrystallized samples, no stage attributable to gas bubbles appeared in the desorption spectrum of the deformed samples demonstrating the strong impact of dislocations on hydrogen retention.

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To cite this version:B Minov, L Dupré, M J Konstantinović. Magnetic after-effect study of dislocation relaxation in Fe-based alloys. Journal of Physics D: Applied Physics, IOP Publishing, 2011, 44 (30) Abstract. Dislocation-related relaxation processes are studied by measuring the magnetic after-effect spectra as a function of temperature in a variety of non-deformed and cold-worked iron alloys. In the α-Fe and Fe-1%Cu alloys the peak centered at about 320 K appears as a consequence of plastic deformation. On the basis of the behavior of its parameters, such as the temperature position of the peak, the full width at half maximum, and the integrated intensities, this feature is assigned to the relaxation process of thermally-activated dislocation motion.

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Carbon distribution in Fe-Cr-C alloys with a variety of Cr concentrations is studied based on internal friction, optical and transmission-electron microscopy. It is found that the carbon distribution strongly depends on initial microstructure, being ferritic or ferritic/martensitic, which is determined by the thermal treatment, and Cr and carbon concentrations. In the quenched alloys, carbon is observed in the form of small carbon-vacancy complexes, most probably two carbon -single vacancy cluster, 2CV, that dissolve at about 500 K. In tempered alloys, the carbon atoms are observed to be uniformly distributed only in Fe-2.5Cr-C alloy, which is fully ferrite. In the alloys with 5-12% of Cr, with ferritic/martensitic microstructure, carbon-Snoek relaxation peak is not observed due to the carbon precipitation, as well as due to atomic carbon being trapped at dislocations and grain boundaries. In both quenched and tempered alloys, the plastic deformation causes the appearance of the broad relaxation peak close to 300 K which could be assigned to dissolution of single carbon -single vacancy, CV, complexes.