Characterisation of radiation damage in W and W-based alloys from 2 MeV self-ion near-bulk implantations

Abstract

The displacement damage induced in W and W-5 wt.% Re and W-5 wt.% Ta alloys by 2 MeV W + irradiation to doses 3.3×10 17-2.5×10 19 W + /m 2 at temperatures ranging from 300 to 750°C has been characterized by transmission electron microscopy. An automated sizing and counting approach based on Image J (a Java-based image processing program developed at the National Institutes of Health) [1] has been performed for all near-bulk irradiation data. In all cases the damage comprised dislocation loops, mostly of interstitial type, with Burgers vectors b = ½<111> (> 60%) and b = <100>. The diameters of loops did not exceed 20 nm with most being ≤ 6 nm diameter. The loop number density varied between 10 22 and 10 23 loops/m 3. With increasing irradiation temperature, the loop size distributions shifted towards larger sizes, and there was a substantial decrease in loop number densities. The damage microstructure was less sensitive to dose than to temperature. Under the same irradiation conditions, loop number densities in the W-Re and W-Ta alloys were higher than in pure W but loops were smaller. In grains with normals close to z = <001>, loop strings developed in pure W at temperatures ≥ 500°C and doses ≥ 1.2 dpa, but such strings were not observed in the W-Re or W-Ta alloys. However, in other grain orientations complex structures appeared in all materials and dense dislocation networks formed at higher doses.

Precipitate Stability in a Zr–2.5Nb–0.5Cu Alloy under Heavy Ion Irradiation

“…Therefore, the defects in thin and thick samples can be expected to be different. However, for fast heavy ion irradiation, no difference was observed in a recent study in W [48], likely because the defect size is generally small in heavy ion irradiation. Our irradiation was carried out using rapid heavy ion irradiation conditions (around 10 min for 1 dpa).…”

In-situ TEM studies of 150 keV W+ ion irradiated W and W-alloys: Damage production and microstructural evolution

“…Ciupi nski et al [26] and Yi et al [27] have used self-ion irradiation to study trends with dose (0.01e30 dpa) and irradiation temperature (300e1023 K) for <001>-grains 1 [28] of W and W-alloys, utilising cross-sectional and planar specimen geometries respectively. Both sets of authors confirmed that in Stage II, loops with b ¼ ½ <111> (~75%) and b ¼ <100> coexist, and were mostly 6 nm in diameter and interstitial in nature [22].…”

Thermal Evolution of the Proton Irradiated Structure in Tungsten–5 wt% Tantalum

“…Interstitial-type dislocation loops form at those low irradiation temperatures in W-Ta alloys. The loop size is smaller and the loop number density is higher than in tungsten under equivalent irradiation conditions [19]. The low-temperature irradiation-hardening due to dislocation loops saturates at a damage level of 13 dpa at 300°C [20].…”

“…The low-temperature irradiation-hardening due to dislocation loops saturates at a damage level of 13 dpa at 300°C [20]. Ta is predicted to have a repulsive interaction with self-interstitial atom (SIA) defects such as \111[ crowdion [21] and dumbbell [22] configurations, and potentially restrict the mobility of SIAs and interstitial loops in W [19].…”