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 x 10(17) - 2.5 x 10(19) W+/m(2) at temperatures ranging from 300 to 750 degrees C has been characterised by transmission electron microscopy. An automated sizing and counting approach based on Image J (a Java-based image processing programme 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 = 1/2 < 111 > (>60%) and b = (1 00). 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 = < 00 1 >, loop strings developed in pure W at temperatures >= 500 degrees 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. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.