Mechanical properties and interphase boundary composition of ferritic steels strengthened by yttrium and titanium disperse oxides

Mechanical properties of Fe-13 wt.% Cr-2 wt.% Mo ferritic steels prepared by powder metallurgy methods and strengthened by disperse oxides of Y and Ti are studied as a function of annealing time at 700 °C. Creep-rupture strength of the strengthened steels is 2–3 times higher than that of the same material without dispersoids. The steel with Y2O3 has usually a higher strength and a lower plasticity in comparison with the steel with TiO2. Prolonged annealing at 700 °C causes only moderate changes in the studied properties. Y2O3 particles are chemically inactive in ferritic matrix, whereas TiO2 dispersoids interact with segregated Cr atoms and form complex (Cr,Ti)xOy compounds at the interfaces. The thickness of these layers exceeds tens of nanometers.