The role of oxygen in powder processing of FeAl

The aim of this study is to highlight the role of oxygen and oxides, present in elemental powders or formed during processing, and its effects on consolidated FeAl (40 at.% Al). The subject is tackled by a traditional powder metallurgy route. Both powder and the consolidated material have been characterised by electron microscopy for microstructure, chemical analysis of oxygen content and surface sensitive spectroscopy methods for the chemical state and oxide thickness. The material, produced by mechanical alloying and hot isostatic pressing, HIP, has a fine grained microstructure, 1–5 μm, and contains Al2O3-precipitates corresponding to 770 ppm oxygen. The milled powder is covered both by both A12O3 (80%) and Fe-oxide after air exposure. The nature and thinness of the oxide scale explain the successful use of HIP to consolidate FeAl, both with powder produced in protective argon atmosphere or after air exposure.