Evolution of defects in titanium grade 2 under Ti²⁺ ion irradiation

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao. Key words. Charged particle irradiations, dislocation loops, image analysis, irradiation defect evolution, titanium, transmission electron microscopy. SummaryThe complexity and diversity of microstructure involved in titanium alloys make it rather difficult to quantitatively describe defect evolution due to irradiation. This paper focuses on defect evolutions of commercially pure titanium grade 2 under Ti 2+ ion irradiation considering the effect of dose (0.6 and 3 dpa), temperature (300°C and 430°C) and flux (15:1 ratio). An irradiation damage profile was predicted using SRIM software to obtain a homogeneous damage on at least 500 nm depth for TEM observations and simulated using JANNUS-Saclay facility. The details regarding the quantification methodologies of the defects from dark field images are provided, as are the origins of the associated uncertainties. In addition to a tangled dislocation network, presence of the <a>-type and <c>-component loops is observed. The latter was scarcely reported in the literature in the case of titanium alloys. At low temperature, the size distribution of the <a>-type dislocation loops remained similar regardless of the dose and flux whereas these parameters have highly influence at 430°C. A widening of the size distribution and an increase of the threshold incubation dose (TID) was noted with the temperature. In the case of the <c>-component loops, it was shown that the nucleation occurred in spite of the 0.6 dpa low dose.

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

“…During an irradiation at 300 °C, no notable influence of the dose and flux (for the considered doses and fluxes ranges) was noticed on the <a>-type defects in the Ti6-4 alloy. This phenomenon was already observed by the authors in a commercially pure T40 a alloy [16]. As mentioned previously, the irradiation temperature of 300 ac corresponds to -250 ac in reactor.…”

“…Disk specimens with a diameter of 3 mm and a thickness of 100 µm were irradiated using Ti 2+ ions with an energy of 6 MeV at the JANNUS French platform in a similar way as described in Ref. [16]. The simulation of the damage profile using SRIM (the Stopping and Range of Ions in Matter) software is given on Fig.…”

“…After irradiation, the disk was thinned again to obtain a hole at the center of the disk by electropolishing on the non-irradiated face only (backpolishing). used [16]. As radiation induced defect structures were suspected to be affected by surface effects, a cross sectional sample was also prepared using Focused Ion Bearn (FIB) technique (3 dpa 430 °C) to check this point.…”

“…2), thus no impact of the implanted self-interstitial atoms was ex pected on the observed defect structures. 19 samples can be fully irradiated at the same time during one irradiation [16]. The irra diation was performed in a triple beam chamber using the 2 MV Tandem Pelletron JAPE'J'I' M of the JANNUS facility [17,18].…”

“…The defect distributions were counted by image analysis, using the Noesis Visilog software ™ . After choosing an area on the micrograph, defects were selected and defined manually with a graphie tablet and thus automatically counted and measured as explained elsewhere [16]. It can be noticed that the influence of truncation by foi!…”