The microstructural properties and hardness of a model ternary Fe-4Cr-6Ti ferritic alloy aged at 800°C for 8, 16 and 24 h are investigated in detail. Fine Fe2Ti Laves phase particles precipitate in the α-Fe (ferrite) matrix phase after solutionizing and subsequent aging treatments. The size and amount of Fe2Ti precipitates gradually increase with increasing aging time. The magnetic measurements of the aged samples confirm the variations in the microstructural properties including the volume fraction of the constituent phases, and Ti content of the α-Fe matrix phase. The mean Vickers microhardness value also increases from 203.5 to 238.4 with increasing aging time from 8 to 24 h. In addition, the cyclic oxidation behavior of 24 h aged sample, which contains maximum amount of Fe2Ti precipitates, is also investigated in detail. X-ray diffraction analysis reveals that scale product is α-Fe2O3 (hematite). Significant scale spallation and void formation is observed on the surfaces of 24 h aged Fe-4Cr-6Ti sample oxidized at 500°C.

In present study, Fe-22Cr-4.5Al oxide dispersion strengthened ferritic alloys were fabricated using a pre-alloyed powder with different minor alloying elements, and their microstructures and tensile properties were investigated to develop the advanced structural materials for high temperature service components. Planetary-typed mechanical alloying and uniaxial hot pressing processes were employed to fabricate the Fe-Cr-Al oxide dispersion strengthened ferritic alloys. Microstructural observation revealed that oxide dispersion strengthened ferritic alloys with Ti, Zr additions presented extremely fine micro-grains with a high number density of nano-scaled oxide particles which uniformly distributed in micro-grains and on the grain boundaries. These oxide particles were confirmed as a fine complex oxide, Y2Zr2O7. These favorable microstructures led to superior tensile properties than commercial ferritic stainless steel and oxide dispersion strengthened ferritic alloy with only Ti addition at elevated temperature.