| Abstract Scope |
The hierarchical-structured nanoparticles were introduced into the oxide dispersion strengthened (ODS) ferritic alloy to cooperatively improve the elevated-temperature mechanical properties. A high number density of hierarchical nanoparticles (Y-Al-O oxides, Ni (Al, Mn) intermetallic phase and Cu-rich clusters) with size of 5-13 nm were formed in the peak aged sample. Cu-rich clusters first heterogeneous nucleate at the pre-existing interface of bcc-Fe/oxide, and then Ni, Al and Mn diffuse outwards from the Cu-rich cluster, resulting in the heterogeneous precipitation of B2-Ni (Al, Mn) nanoparticles at the Cu cluster/bcc-Fe interface. With the growth of B2-Ni (Al, Mn) nanoparticles, the oxide/Cu-rich cluster/B2-Ni (Al, Mn) hierarchical-structured nanoparticles were formed. A coherent or semi-coherent nature was revealed between Y-Al-O/bcc-Fe, Y-Al-O/bcc-Cu, bcc-Cu/NiAl and NiAl/bcc-Fe. Owing to the lattice-strain field and the load transfer capability induced by those hierarchical-structured nanoparticles, the mechanical properties of ferritic alloy above 650℃ was improved. |