Crystal structure and morphology of AIN precipitating on nitriding of an Fe-2at.% Al alloy

Abstract

Abstract The crystallography of aluminium nitride precipitating on nitriding of an Fe-2at.% AI alloy has been investigated by electron microscopy and by X-ray diffraction. The precipitation of AIN can be described as a classical nucleation and growth process; no evidence has been obtained for clustering of alloying element atoms or other pre-precipitation phenomena. Two modes of AIN precipitation have been observed depending on the initial deformation state of the specimens: (i) in cold-rolled specimens, precipitation of cubic (rock salt) AIN particles with platelet-type morphology exhibiting a Bain orientation relationship with the α-Fe matrix, and (ii) in recrystallized specimens, precipitation of hexagonal (wurtzite) AIN particles without specific morphology and, for a significant part exhibiting a Pitsch-Schrader orientation relationship with the α-Fe matrix. A small fraction of cubic (rock salt) AIN also occurs in the recrystallized specimens. Although the hexagonal (wurtzite) crystal structure of AI...