Irradiation hardening of stainless steel model alloy after Fe-ion irradiation and post-irradiation annealing treatment

Microstructural observation with atom probe tomography, transmission electron microscopy, and mechanical examination with a nano-indenter were performed on stainless steel model alloy that had been irradiated with Fe ions and subjected to post-irradiation annealing treatment (PIA). Significant irradiation hardening occurred in the as-irradiated specimen and irradiation hardening recovery occurred at 400 °C of cumulative PIA, Tiny black dots, Frank loops and Ni-Si clusters formed in the as-irradiated specimen and their recovery was observed with the cumulative PIA. A classic dispersed-barrier hardening model was used to evaluate irradiation hardening connected to microstructural information by applying the density and size of defect variants. Ni-Si clusters and Frank loops contributed substantially to the increase of irradiation hardening, whereas the black dots contributed little for the stainless steel model alloy. The barrier strength factor of Ni-Si clusters, αSC, was obtained as 0.029 and 0.015 for two different obstacle strength model, which suggests that an individual Ni-Si cluster is a weak barrier obstacle to mobile dislocation on the dispersed-barrier hardening model, but that the dense formation of Ni-Si clusters controls irradiation hardening behavior. A quantitative analysis was performed of the increase in strength from the Ni-Si clusters that was caused by coherency strains, and an irradiation hardening mechanism for the stainless steel, including the solute atom clusters, is discussed.