Microstructural evolution of He-preinjected austenitic stainless steels under HVEM irradiation

Two kinds of austenitic stainless steels, 316R (standard type 316 stainless steel) and alloy K (low-C and 0.29 wt% Ti) were irradiated in a high voltage electron microscope (HVEM) after He injection to 2.5 and 10 appm. 45 keV He was injected into the prepared transmission electron microscope (TEM) foils and HVEM irradiation was performed at 773 K to 14 dpa. Without helium preinjection, alloy K shows very few void production and thus the void swelling of alloy K was lower than that of 316R. Injected helium of 2.5 and 10 appm led to the void number densities of 1022/m3 level or more in both steels. Void swelling was largest for 2.5 appm He specimens for both steels and the void growth rate was higher in alloy K than in 316R, and void swelling was higher in alloy K. The order of swelling resistance of these two steels as thus changed after 2.5 appm He injection. ((orig.))