Small-angle neutron scattering quantification of phase separation and the corresponding embrittlement of a super duplex stainless steel after long-term aging at 300°C

Small-angle neutron scattering (SANS) was applied to quantify the nanostructural evolution during spinodal decomposition in a 25Cr-7Ni (wt.%) super duplex stainless steel isothermally aged at 300 °C, for up-to 48,000 h. Prior to the application on the 25Cr-7Ni alloy, the SANS methodology was validated by comparing results from SANS measurements on binary Fe-Cr alloys with atom probe tomography results. SANS results on the 25Cr-7Ni alloy indicated that decomposition wavelength decreased from 5.1 nm to 4.5 nm, whereas the amplitude increased from 15.0 to 33.4 at.%. This quantitative nanostructural evolution correlated to a hardening of the ferrite phase by 190 HV and a reduction of the sub-size Charpy-V impact toughness from 60 J to 25 J