Microstructures and tensile properties of an austenitic ODS heat resistance steel

In this study, an austenitic oxide dispersion strengthened (ODS) heat resistance steel with added Y2O3 is fabricated by process of mechanical alloying (MA) and hot isostatic pressing (HIP). The proceeded steel exhibits an ultrafine-grained (UFG) microstructure with a bimodal grain size distribution. Numerous nano particles located inside the grains are precipitated with an average size of 8.77 nm. Most particles exhibit a gathering structure with the Y-rich phase wrapped around the Cu-rich phase. The Y-rich phase is identified as Y2O3 that is semi-coherent with the austenitic matrix. The existence of the Cu-rich phase is favorable for the Y2O3 precipitation. Mechanical properties tests at RT and 650 °C reveal a great improvement in strengths over the commercial Super304H austenitic heat resistance steel due to the presence of the ultrafine grains and numerous oxide nano particles. The higher tensile strength makes this austenitic ODS heat resistance steel as an excellent candidate material for high-temperature applications.