Development of oxide dispersion strengthened ferritic steels with and without aluminum

Abstract

Pure Fe, Cr, Al, Ti elemental powders and pre-alloyed Y₂O₃ powder were processed by high energy mechanical milling. The compositions of the mixed powders are designed as Fe-18Cr-0.2Ti-0.35Y₂O₃ and Fe-18Cr-5Al-0.2Ti-0.35Y₂O₃ in weight percent. The as-milled powders were consolidated by hot extrusion at 1423 K. The dispersed oxide particles were identified to be titania+ yttria for Al-free oxide dispersion strengthened (ODS) steel and alumina+ yttria for Al-added ODS steel, respectively. The ultimate tensile strength of Al-free ODS steel was higher than that of Al-added ODS steel over the temperature range of 298–973 K, because of the difference in number density and size of thermally stable oxide particles dispersed in both steel matrices. The strength in the longitudinal direction was lower than that in the transverse direction, probably due to anisotropy of the microstructure with elongated grains in the hot-extrusion direction for the 18%Cr-ODS steels with and without 5%Al.

Key words： oxide dispersion strengthened (ODS) steel; milling; extrusion; aluminum; yttria

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