Hardening and ductility loss of RAFM steel CLF-1 irradiated with high-energy heavy ions

Irradiation induced hardening and ductility loss of a Chinese reduced-activation ferritic / martensitic steel CLF-1 is evaluated by utilizing the high-energy heavy ion irradiation and the subsequent miniature specimen test technique. Specimens were irradiated with high energy 14N6+ and 56Fe17+ ions supplied by a cyclotron to generate a quasi uniform atomic displacement damage plateau from surface to a depth about 25 μm. Three successively increasing damage levels (0.05, 0.1 and 0.2 dpa) were approached at a low temperature around 223 K. The small punch test at room temperature showed that the ductility loss can be observed at the lowest damage level and increases with the increasing damage level, similar to the variation trend of yield stress with irradiation dose. The TEM observation revealed that the average size and number density of irradiation-induced defect clusters also increased with displacement damage. Assuming that the hardening is caused by the self-interstitial-type dislocation loops, an estimation by combining the numerical calculation of the number density / mean diameter of dislocation loops with the dispersion barrier hardening model yields a similar dose dependence of the irradiation hardening.