Nanoscale characterisation and clustering mechanism in an Fe–Y2O3 model ODS alloy processed by reactive ball milling and annealing

Reactive ball milling and annealing is proposed as a new production method for oxide dispersion strengthened (ODS) steels. A highly concentrated Fe–38 atm.% Y2O3 ODS model alloy was processed by reactive ball milling and annealing of YFe3 and Fe2O3 powders so as to induce the chemical reaction 2YFe3 + Fe2O3 → 8Fe + Y2O3. The model alloy was characterised after milling and annealing by complementary techniques, including atom probe tomography. Ball milling up to the stationary state results in the formation of two metastable nanometric interconnected phases: super-saturated α-iron and an yttrium and oxygen rich phase. Annealing leads the system towards equilibrium through: (i) a chemical evolution of each phase to nearly pure α-Fe and Y2O3 oxide slightly sub-stoichiometric in oxygen; and (ii) growth of the phases. A pure iron matrix reinforced by nanometric Y2O3 particles was successfully synthesised by reactive ball milling and annealing.