Dispersion Strengthened FeCrAlY Alloys by Flake Powder Processing

Abstract

A novel, high yield, powder metallurgy technique involving high energy (attritor) milling was utilized to produce oxide dispersion strengthened FeCrAlY alloys without the concurrent formation of chromia or chromiacontaining spinels. The technique utilizes attritor milling of atomized powder/organic surfactant slurries, in air, to produce flake-like shaped particles with large specific surface areas. It is the oxidation of these powder surfaces under ambient conditions that ultimately generates the dispersoid. Consolidation of powder compacts was accomplished by hot extrusion at either 982'C or 1093'C. The disperso present in as-extruded bar was identified as 3Y203' 5A1203 (yttrium-alu$num garnet) with an average particle size of about 300A. As-extruded 982'C tensile and stress rupture properties were significantly improved when compared to the same composition without dispersoid. id Further improvement in stress-rupture strength was obtained by producing coarse grain structures with high aspect ratio. Two of the alloys produced responded to secondary grain growth in the as-extruded condition by both isothermal annealing and directional recrystallization.