Relationship between hardening and damage structure in austenitic stainless steel 316LN irradiated at low temperature in the HFIR

An austenitic stainless steel 316LN irradiated to damage levels of about 3 dpa at irradiation temperatures of about 90 degrees C and 250 degrees C has been examined by transmission electron microscopy. The irradiation at 90 d egrees C and 250 degrees C induced a dislocation loop density of 3.5 x 10(2 2) and 5.2 x 10(22) m(-3) and a black dot density of 2.2 x 10(23) and 1.1 x 10(23) m-3 respectively, in the steel. A low density (<1 x 10(19) m(-3)) o f radiation-enhanced precipitates was observed in the matrix. No cavities w ere observed. These features are correlated with the changes in tensile pro perties. It is concluded that the dislocation loops and the black dots caus e irradiation hardening and a decrease in the uniform elongation in the 316 LN steel irradiated at low temperatures. (C) 1999 Elsevier Science B.V. All rights reserved.