Evolution of defects in Ti6-4 under Ti2+ ion irradiation: Focus on radiation-induced precipitates

Ion irradiations on the Ti6-4 titanium alloy were conducted at the JANNUS French platform in two different conditions of temperatures, doses and fluxes, to simulate neutron irradiation damage. Quantification of defects and chemical microanalyses were carried out thanks to Transmission Electron Microscopy and Atom Probe Tomography. -type loops and radiation induced precipitates (a vanadium-rich β BCC phase) were observed for both irradiation temperatures. During an irradiation at 300 °C, there was no notable influence of the dose and flux for the considered doses and fluxes ranges on the -type defects. The influence of raising the irradiation temperature up to 430 °C was a lowering of their density and an increase of their mean diameter for both defects. In addition, a lower flux seemed to enhance this temperature effect. These phenomena were very significant for precipitates whereas it appeared very modest for -type loops. The probable mechanism to explain the distribution of vanadium-rich β precipitates inside the α phase is the heterogeneous nucleation. The nucleation is dominated by the Radiation Induced Segregation (RIS) phenomenon at 430 °C and could be dominated by the mechanism of vanadium-rich clusters formation by ballistic effects in the cascades at 300 °C

Etude du fluage à 750ʿC d'alliages Ti48 AI48Cr2Nb2 obtenus par les voies métallurgie des poudres et fonderies

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Plasticité d'alliages renforcés par nano-précipitation

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

Correlation of radiation-induced changes in microstructure/microchemistry, density and thermo-electric power of type 304L and 316 stainless steels irradiated in the Phénix reactor

International audienc

Precipitation kinetics of oxide dispersion strengthened steels for their application as cladding material in Gen. IV power plants

International audienc

Nano-oxide precipitation kinetics during the consolidation process of a ferritic oxide dispersion strengthened steel.

International audienceOxide Dispersion Strengthened (ODS) steels are candidates for nuclear applications. ODS are produced by mechanical alloying of Fe-14Cr, Y2O3 and TiH2 powders and consolidation at 1100°C, resulting in finely dispersed nano-oxides. Their precipitation kinetics has been quantitatively determined by in-situ Small Angle X-ray Scattering during continuous heating up to 1100°C. Clusters, found in the as-milled state start growing at 450°C until 1100°C, while almost no coarsening was recorded during subsequent isothermal annealing. The nano-oxides resulting from these in-situ experiments were found to be representative of those in materials processed by hot isostatic pressing and hot extrusion. Graphical abstract Main matter Ferritic Oxide Dispersion Strengthened (ODS) steels were developed for applications where a good resistance to harsh environment is required such as generation IV nuclear fission [1] or nuclear fusion power plants [2]. Their Fe-Cr ferritic matrix gives them a good swelling resistance under irradiation [3,4] as well as a good corrosion resistance [5,6]. Nano-precipitates of Y-Ti-O lead to high yield strength and high improvement of thermal creep resistance [7-10] as these nano-oxides act as strong pinning points for both grain boundaries and dislocations, even at high temperatures [7-9,11-13]

The impact of outgassing on the nano-oxides kinetics of ferritic oxide dispersion strengthened steel

International audienceOxide Dispersion Strengthened (ODS) steels are studied for their application in fission and fusion nuclear powerplants. These steels are processed by powder metallurgy involving a high energy milling of Fe-Cr with oxidespowders, followed by outgassing and hot consolidation. The temperature increase during these last two stagestriggers the precipitation of a fine dispersion of nano-oxides. The outgassing stage is generally conducted attemperature between 300 and 800 ◦C for several hours, which can already trigger the formation of nano-oxides,and thus may have an influence on the final nano-oxide characteristics. In this work we assess the nano-oxidessize by Small Angle X-Ray Scattering (SAXS) and get insight on the nano-oxides chemical and structural properties by comparison between SAXS and Atom Probe Tomography (APT) during a thermal treatment at 700 ◦C for5 h, simulating the outgassing stage. We show that despite that the nano-oxides slightly grow during the 700 ◦Cheating, the final properties of the nano-oxides in term of size and number density are extremely close to thosewhere no 700 ◦C isothermal was applied. Moreover, the growth rate of the nano-oxides is surprisingly higher at700 ◦C than 1100 ◦C. APT and SAXS comparison shows that the nano-oxides do not stabilize in terms of stoichiometry and structure in the studied conditions, and that a small quantity of Al remain in the precipitatesduring this 700 ◦C isothermal treatment. Both of these factors could influence the nano-oxides kinetics at lowtemperature

Stability of nano-oxides upon heavy ion irradiation of an ODS material

International audienc

Amorphization of oxides in ODS materials under low and high energy ion irradiations

International audienc