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 signicantly 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 benecial 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...
»