The effects of intermediate temeprature irradiaiton on the mechanical behavior of 300-series austenitic stainless steels

Data in the literature on the microstructures and mechanical properties of solution annealed 300-series austenite stainless steels irradiated under conditions relevant to the design of near term fusion reactors show consistent trends for a variety of alloys and environments. The yield stress increases rapidly approaching a saturation value of about 850 ± 100 MPa, essentially identical to the ultimate stress. Visible irradiation-induced features, which are predominantly helium bubbles and dislocations loops, can account for only about 50 to 70% of these increases. The uniform elongation is reduced to less than 1% due to the decrease in strain hardening and severe flow localization following irradiation. The fracture toughness also decreases to values near or below 50 MPa m1/2. A simple critical strain model is shown to be quantitatively consistent with the observed toughness trends. These results suggest that more rigorous fracture models can be developed to permit quantitative predictions of toughness changes based on a variety of measurements made on small specimens. (orig.)