Developing Core-Shell Nano-Structures in FeCrAl-ODS Ferritic Alloys with the Co-Addition of Ni and Zr

A new Ni + Zr co-alloyed FeCrAl-ODS (oxide-dispersion-strengthened) ferritic alloy was fabricated by ball-milling and hot-isostatic-pressing. Using electron microscopy and atom probe tomography, the dispersive formation of high density core-shelled nano-particles of various sizes was confirmed with a common B2-NiAl shell. Among which, median-sized nano-particles (20-50 nm) typically have an Y4Al2O9 nano-core of < similar to 20 nm, ultra-fine nano-particles (< similar to 20) nm have an Y4Zr3O12 nano-core of < similar to 10 nm, and larger-sized nano-particles (50-100 nm) incorporate an ultra-fine Y4Al2O9 nano-core and a few ultra-fine Y4Zr3O12 nano-oxides. All these nano-phases were highly coherent with the ferritic matrix. No large Y-Al-O nano-oxides were formed. The total number density of ultra-fine nano-particles was estimated as similar to 2 x 10(23) m(-3) with a mean size of 6.3 nm only, and accordingly, the new alloy achieved an excellent combination of strength and ductility at high temperatures.