Effect of Zr on the irradiated microstructure and hardening in 304 stainless steel

Model alloys of 304 Stainless Steels (SS) (Fe-18Cr- 9.5Ni-1.75Mn) and 304 SS+Zr (Fe-18Cr-9.5Ni- 1.75Mn+0.04Zr and Fe-18Cr-9.5Ni-l. 75Mn+ 0.16Zr) were irradiated with 3.2 MeV protons to a dose of 1.0 dpa at 400°C. Following irradiation, the microstructure was characterized. The number density, defect size, and size distributions for faulted loops and voids were determined. Swelling for each irradiation condition was calculated based on the void measurements. The effect of Zr addition on the irradiated microstructure and hardening is clearly demonstrated. The number density of defects decreased with the Zr addition while the size change of faulted loops and voids is less pronounced. Radiation hardening was reduced by Zr addition. Void swelling is decreased with Zr addition. The reduction in void density and swelling may be caused by the enhanced recombination of defects at oversized Zr solute atoms, suppressing the vacancy super saturation and therefore directly suppressing void nucleation. The reduction in loop density is believed due to the enhanced point defects recombination caused by oversized solute Zr.