Irradiation response of ODS ferritic steels to high-energy Ne ions at HIRFL

Two kinds of ODS high-Cr ferritic steels (commercial MA956 and an Al-free 16Cr-0.1Ti ODS ferritic steel) and one conventional ferritic/martensitic steel (T122) were irradiated at about 440 degrees C with high-energy Ne-20-ions in HIRFL. Successively increasing doses from 350 to 900 appm of Ne concentration, corresponding to atomic displacement levels from 0.7 to 1.8 dpa, were approached. A nearly uniform distribution of Ne concentration and atomic displacement damage was produced through the thickness of 60 mu m of the specimens by using an energy degrader. Mechanical properties of the specimens were tested with the small-ball punch technique. The test at room temperature shows a less significant ductility loss in the ODS ferritic steel MA956 than in the T122 irradiated to the same dose of 350 appm Ne/0.7 dpa. The test at 500 degrees C shows that the Al-free 16Cr-0.1Ti ODS ferritic steel does not exhibit observable loss of ductility even to the highest dose level (900 appm Ne/1.8 dpa). An investigation with transmission electron microscopy (TEM) shows that voids with a diameter up to 70 nm were formed at grain boundaries in the conventional ferritic/martensitic steel T122 while only smaller bubbles were formed at the oxides/substrate interfaces in the ODS ferritic steel MA956. Mechanisms underlying the difference of irradiation response of the steels are discussed. (C) 2014 Elsevier B.V. All rights reserved.