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

Abstract

a b s t r a c tIn-situ irradiations with 150 keV W þ ions have been performed on W and W-5wt.% (Re; Ta; V) alloys in a comprehensive study of the influences of irradiation temperature T irr , dose, alloying elements and grain orientations on radiation damage production and microstructural evolution. For T irr between 30 K and 1073 K, the first observable defects in pure W appeared at doses 0.01 dpa, and were most likely vacancy loops, with Burgers vectors predominantly of type b ¼ ½ <111>. With increasing T irr , the retained defect concentration decreased strongly and the maximum cluster size increased from~1300 point defects at 30 K to~2300 point defects at 1073 K. At all irradiation temperatures, the evolution of damage microstructures with dose from 0.1 to 1.0 dpa involved defect cluster migration, with mutual elastic interactions often leading to spatial inhomogeneities and loop reactions. In pure W, spatial ordering of loops was observed at doses >0.4 dpa and T irr ! 773 K in grains close to z ¼ <001>. No such ordering was found in similar grain orientations for the W-(Re; Ta) alloys, but it was found in the non-z ¼ <001> grains. Post-irradiation analysis on W and W-5 wt% (Re; Ta) at 1.0 dpa showed that ½ <111> and <100> loops of both vacancy and interstitial type were present, at number densities~10 15 loops m À2 . In all cases ½ <111> loops were dominant, the fraction of these with interstitial nature increased with T irr , and the proportion of <100> loops decreased with increasing T irr . Compared with pure W, microstructures in the W-(Re; Ta) alloys exhibited higher loop number densities and evolved more quickly with increasing dose towards damage saturation.

Machine-learning interatomic potential for radiation damage and defects in tungsten

“…15 correspond to symmetric configurations. The 1/2 1 1 1 loop is the most stable planar configuration for sizes above around 40 vacancies, consistent with experimental observations of (both interstitial and vacancy) dislocations loops [84]. For dislocation loops, only energies of stable sizes are shown in Fig.…”

“…For tungsten, the majority of existing potentials struggle to reproduce the correct trend of the relative stability of clusters of multiple SIAs. For example, several widely used EAM potentials predict dislocation loops with the Burgers vector 1 0 0 to be lower in energy than the 1/2 1 1 1 loops [5], which is in clear contradiction to DFT [82] and experimental observations [83,84]. We therefore put particular focus on ensuring that our GAP reproduces the expected trend obtained by DFT.…”

Outstanding radiation resistance of tungsten-based high-entropy alloys

“…Therefore, there are seven possibilities of Burgers vector variants (4 for <111> type and 3 for <100> type). In W related materials, <111> type Burgers vector have been observed at 1073 K. 33,35,36 Under any diffraction condition, using the g.b invisibility criteria, at least 50 % of the <111> loops should be observed in the TEM image. However, in our samples, several grains showed no black spots (e.g.…”

Elastic interactions between nano-scale defects in irradiated materials

“…Electron microscope observations of microstructures due to irradiation [20,21,22,23,24,25,26] show that at any moment most loops are separated by distances greater than their size. Reactions between loops, resulting in their 60 annihilation or coalescence, and occurring only when the distance between them is virtually zero, typically involve a small faction of all the defects present in the material.…”

“…Rafts of defects are routinely observed experimentally in materials exposed to irradiation [20,21,22,23,24,25,26].…”