Nanometer scale precipitation in ferritic MA/ODS alloy MA957

The microstructure of a commercial mechanically-alloyed oxide dispersion strengthened MA957 alloy has been characterized in the as-received condition and after annealing for up to 24 h at 1300 °C (∼0.85 Tm) by atom probe tomography and electron microscopy. Atom probe tomography revealed a high number density of ultrafine 2-nm-diameter Ti-, Y- and O-enriched particles in the ferrite matrix in the as-received condition. The size increased and the number density of these particles decreased during the annealing treatment for 1 and 24 h at 1300 °C. Some coarser (∼10 nm) Ti-, Y- and O-enriched precipitates were also observed at the grain boundaries. No significant grain growth or recrystallization was observed during the high temperature annealing treatment.