Dislocation structure of tungsten irradiated by light ions

Abstract

Single crystalline tungsten samples were irradiated by He, D, and H at room temperature, with a calculated damage level in the peak maximum up to 0.04 dpa and with He up to 0.5 dpa. The dislocation structure of the whole damage zone was investigated perpendicular to the irradiated surface by transmission electron microscopy under four different two-beam diffraction conditions g= -200, 020, -110, 110 close to the [100] zone axis, taking bright-field kinematical images. The depth of the damage zone observed by Transmission Electron Microscopy is in good agreement with the damage depth calculated by SRIM. The damage zones of the tungsten samples irradiated by He, D, H up to 0.04 dpa can be subdivided into four subzones. Significant differences in the dislocation structures between the different ion species despite comparable calculated damage levels were found at the depth close to the damage peak maximum. In this depth, the damage zone of tungsten irradiated by He consists of small dense dislocation loops (≤ 3 nm) with high strain fields. Irradiation by D creates large dislocation loops with an average diameter of 15-22 nm depending on the set diffraction condition. The damage zone of H-irradiated tungsten is dominated by long dislocation lines at the depth of the damage peak maximum. No transition from dislocation loops to lines was found in the sample irradiated with He up to 0.5 dpa. This is probably due to He bubbles, which hinder the loops to aggregate into lines. This work shows that the displacement damage obtained by the irradiation of tungsten at room temperature with light ions is significantly different to tungsten irradiated to the same calculated damage level by medium to high-mass ions [B. Wielunska et al., Nucl. Fusion 62 (2022) 096003].

Effect of high-energy Ne ions irradiation on mechanical properties difference between Zr63.5Cu23Al9Fe4.5 metallic glass and crystalline W

“…The corresponding fitting curves are shown in figure 8(b), and is given in table 3. was ~6.02 GPa before irradiation, ~5.89 GPa after irradiation at the dose of 6.5×10 14 Ne/cm 2 , and ~5.50 GPa after irradiation at the dose of 2.6×10 15 Ne/cm 2 . In contrast to the irradiation hardening of crystalline W, Zr 63.5 Cu 23 Al 9 Fe 4.5 MG softened after irradiation and its hardness decreased with the increasing ion dose.…”

“…Before irradiation, two materials were cleaned by ultrasound with alcohol. The experiment of high-energy Ne ions irradiation was performed on the medium energy irradiation terminal (SFC-T1) of the national laboratory of heavy ion research facility (HIRFL) in the Institute of Modern Physics in Lanzhou, China, with the ion energy of 28.8 MeV, the flux of 1.2×10 11 ions/(cm 2 •s) and the doses of 6.5×10 14 Ne/cm 2 and 2.6×10 15 Ne/cm 2 . The diameter of the irradiated area was 18 mm and the chamber was maintained at a vacuum of 2.3×10 −5 Pa.…”

“…Figure 1 shows the SRIM simulation results of two materials after Ne ions irradiation at the dose of 2.6×10 15 Ne/cm 2 . The ions concentration distribution curves were Gaussianlike, while the displacement damage curves showed the shape of Bragg curves with a wide front and a narrow back (figure 1(a)).…”

“…By comparing the magnified images of the diffraction peak of (110) (figure 3(b)), it can be seen that the diffraction peak of the irradiated crystalline W shifted to the lower angle, indicating tensile stresses generated within the crystalline W after irradiation, which caused the interplanar spacing to increase. Based on the Williamson-Hall analysis [15], the contribution of lattice strain ε generated by lattice defects can be separated from the half-peak width β of each diffraction peak, expressed in equation ( 1),…”

“…Figure 3(c) shows the Williamson-Hall curves of crystalline W before and after irradiation. The grain size of W was 141 nm before irradiation, which was 109 nm and 138 nm after irradiation at the dose of 6.5×10 14 Ne/cm 2 and 2.6×10 15 Ne/cm 2 . The lattice strain generated by lattice defects in pristine crystalline W was ~5.13×10 −4 , which became higher after irradiation and increased with the dose from ~6.32×10 −4 to 8.61×10 −4 .…”