Oxide dispersion strengthened (ODS) steels with different contents of zirconium (denoted as 16Cr ODS, 16Cr-0.3Zr ODS and 16Cr-0.6Zr ODS) were fabricated to investigate the effects of Zr on strengthening mechanism of Al-alloyed 16Cr ODS steel. Electron backscatter diffraction (EBSD) results show that the mean grain size of ODS steels could be decreased by Zr addition. Transmission electron microscope (TEM) results indicate that Zr addition could increase the number density but decrease the mean diameter and inter-particle spacing of oxide particles. Furthermore, it is also found that in addition to Y-Al-O nanoparticles, Y-Zr-O oxides with finer size were observed in 16Cr-0.3Zr ODS and 16Cr-0.6Zr ODS steels. These changes in microstructure significantly increase the yield strength (YS) and ultimate tensile strength (UTS) of ODS steels through mechanisms of grain boundary strengthening and dispersion strengthening.

To study the effects of various types of precipitates and precipitate evolution behavior on austenite (size and phase fraction) in reduced activation ferritic/martensitic (RAFM) steel, RAFM steel was heated to various austenitizing temperatures. The microstructures of specimens were observed using optical microscopy (OM) and transmission electron microscopy (TEM). The results indicate that the M₂₃C₆ and MX precipitates gradually coarsen and dissolve into the matrix as the austenitizing temperatures increase. The M₂₃C₆ precipitates dissolve completely at 1100 °C, while the MX precipitates dissolve completely at 1200 °C. The evolution of two types of precipitate has a significant effect on the size of austenite. Based on the Zener pinning model, the effect of precipitate evolution on austenite grain size is quantified. It was found that the coarsening and dissolution of M₂₃C₆ and MX precipitates leads to a decrease in pinning pressure on grain boundaries, facilitating the rapid growth of austenite grains. The austenite phase fraction is also affected by the coarsening and dissolution of precipitates.

Oxide dispersion strengthened tungsten (ODS-W) alloy was prepared by chemical method, conventional sintering and hot-rolling method, which breaks through the research bottleneck of preparing tungsten alloys with excellent comprehensive mechanical properties. More specifically, it can exhibit ultrahigh strength and superior toughness when tested at 200°C. In addition, the nil ductility temperature (NDT) can also dramatically decrease to 100–150°C. The bimodal structure formed by the uneven distribution of yttria and the lamellar structure formed by hot rolling in this ODS-W alloy provide a feasible way to develop other engineering materials with ultra-high strength and ductility. GRAPHICAL ABSTRACT IMPACT STATEMENT W-Y₂O₃ alloy with bimodal and lamellar structures prepared by wet chemical method and hot rolling process exhibits excellent combination of ultra-high strength and toughness.