Nanocrystalline ODS-iron aluminide by cryo-milling: Consolidation, microstructure and mechanical behavior

Nanocrystalline oxide dispersion strengthened (ODS) Fe-25at%Al alloy was produced by cryo-milling of elemental powder blend with stoichiometric composition and Y2O3. The as-synthesized powder was subsequently consolidated by hot extrusion and microstructural and mechanical properties were evaluated on heat treated bulk sample. In spite of substantial ductility, the compressive strength of the fabricated alloy is considerably high. Such improved mechanical behavior was attributed to the much-refined particle size as well as crystallite size of the milled powder under cryo-milling when compared to that achievable by conventional high-energy ball milling. The cryo-milled powder structure eventually led to a comparatively finer microstructure in the as-extruded bulk material. The finer powder structure also ensured a better distribution of the nanostructured Y2O3 dispersoids and other nanostructured phases formed in situ viz. Al2O3, AlN, etc., bringing in additional improvement of the mechanical properties.