In situ synchrotron tensile investigations on the phase responses within an oxide dispersion-strengthened (ODS) 304 steel

Austenitic oxide dispersion-strengthened (ODS) alloys provide excellent mechanical strength and radiation tolerance along with their intrinsic advantages in corrosion resistance and high temperature creep resistance. This paper reports the in situ synchrotron X-ray diffraction (XRD) tensile test results of ODS 304 stainless steel specimens. The oxygen-enriched nanoparticles were first characterized by both atom probe tomography (APT) and analytic scanning transmission electron microscopy (STEM). Three different types of precipitate phases were recognized, including large scale (around 100 nm) TiN, intermediate scale (around 20 nm) Y-Al-O, and small scale (<5nm) Y-Ti-O. The lattice responses of different phases within the alloy to the externally applied stress indicate a prominent load partitioning phenomenon. This phenomenon was found to be highly dependent on the size of the precipitates. In addition, deformation-induced martensitic transformation was examined by the modified Williamson-Hall analyses of peak broadening, and was found to be different from that in ordinary 304 stainless steel.