Effect of Argon Ion Irradiation on Hardening and Microstructure of Ferritic-Martensitic Steel T91

Abstract

Ferritic-martensitic steel T91 was irradiated with 1.4 MeV Ar+ ions to doses from 0.5 to 7 displacements per atom (dpa) at room temperature. Microstructure characterization was performed using transmission electron microscopy (TEM). TEM observations indicated that black dots and dislocation loops dominated the damage microstructure after ion irradiation. The nanoindentation technique was used to find out the changes in the hardness values with irradiation dose. Nanoindentation tests were performed at room temperature in continuous stiffness measurement mode before and after the irradiation. Nix-Gao model was used to extract the bulk-equivalent nanohardness of specimens. Pile-up of material around the indentation site that affects the calculated contact area was taken into account for correct interpretation of the mechanical properties of the irradiated material. It is shown that ion irradiation leads to hardening by 21% (∆H ~ 0.7 GPa) which reaches quasi saturation at doses ≥1 dpa.