High-temperature damage evolution in 10 keV He+ irradiated W and W-5Re

High-temperature damage evolution in pure W and W-5Re has been studied by combining transmission electron microscopy and in-situ irradiations with 10 keV He+ ions. The irradiations covered a temperature range of Tirr = 773-1473 K and a fluence range of (4.5-15) × 1019 He+/m2. In pure W, detailed characterizations have shown that damage evolution is highly dependent upon the foil thickness. Regions of thickness < 100 nm featured helium bubbles almost exclusively. With increasing Tirr from 773 K to 1473 K, a pronounced bubble growth and an increased degree of bubble ordering were observed. In thicker regions (≳100 nm), 1/2〈111〉 dislocation loops and line entanglements were found up to 1473 K, and were often seen to be decorated with helium bubbles. In W-5Re, areas of different foil thickness exhibited only small differences in damage evolution. The densities of bubbles were comparable to those seen in pure W at all temperatures, while the average size of bubbles was found to be ~10-40% higher. The damage microstructure transformed from a mixture of dislocation loops and bubbles at 773 K to dislocation line entanglements decorated with bubbles at 1473 K.