The development of a composite microstructure with hard aluminum nitrides (AlN) dispersed in a soft ferritic iron-based solid is achieved through the powder metallurgy route. Fe-4.6 at% Al alloy powders subjected to two different thermochemical treatmen ts viz. nitriding and nitriding followed by hydrogen reduction are co nsolidated by spark plasma sintering (SPS) at 900  C. The nal sintered microstructu re is characterized with the help of optical, scanning electron, and transmission electron microscopy along with X-ray diffraction for detailed phase analysis. The microstructures of the nitrided and sintered com- pacts are observed to be signicantly affected by two factors: 1) presence of oxide phases on the surface of the powder particles before SPS and 2) evolution of nitrogen gas due to dissociation of iron nitrides during sintering. These result in a very complicated microstructure. However , for nitrided powders, performing a hydrogen reduction step before SPS lead to a microstructure composed of precipitation-hardened particle cores due to dispersion of nanosized AlN precipitates, with a soft, ferritic interparticle region. This composite micro- structure achieved through the powder metallurgy route, which can be nely tuned by controlling the nitriding, oxidation, and sintering parameters, is envi- sioned to be greatly benecial for several engineering applications such as automotive components    «

The development of a composite microstructure with hard aluminum nitrides (AlN) dispersed in a soft ferritic iron-based solid is achieved through the powder metallurgy route. Fe-4.6 at% Al alloy powders subjected to two different thermochemical treatmen ts viz. nitriding and nitriding followed by hydrogen reduction are co nsolidated by spark plasma sintering (SPS) at 900  C. The nal sintered microstructu re is characterized with the help of optical, scanning electron, and transmiss...    »