Effects of radiation on spinodal decomposition of ferrite in duplex stainless steel

Duplex stainless steel specimens embrittled by temperature-accelerated thermal aging at 400 °C for 40,000 h were irradiated at 300 °C to 1 dpa with 6.4 MeV Fe3+ ions to study the effects of radiation on spinodal decomposition of ferrite. The microstructural change was examined by atom probe tomography, and the hardness change was measured with an ultra-micro hardness tester. Hardening of the ferrite in thermal aged specimens was reduced by irradiation, whereas the ferrite of the unaged specimen was hardened by it. The spinodal decomposition of the ferrite into Fe-rich α phase and Cr-rich α′ phase, and G-phase precipitation occurred after the thermal aging. Fluctuation of the Cr concentration based on the formation of Cr-rich α′ phase decrease by irradiation. This suggested that irradiation caused the disappearance of spinodal decomposition. The decrease in spinodal decomposition correlated with a decrease in hardness.