MECHANICAL ALLOYING OF FE-AL INTERMETALLICS IN THE DO3 COMPOSITION RANGE

Binary Fe-Al intermetallics with compositions ranging between 10 and 30 at % have been produced by mechanical alloying. The elemental powders were milled together resulting in the dissolution of the Al atoms into the Fe lattice. Subsequent heat treatment of the compacted powder resulted in the formation of the intermetallic. However, complete suppression of the DO3 (Fe3Al) structure in favour of the B2 (FeAl) structure was observed. The suppression of the DO3 structure is considered to be due to the presence of the high density of defects resulting from the heavy deformation incurred during milling. At Al compositions below 22 at %, X-ray diffraction revealed a b c c phase with lattice parameters varying between those of alpha-Fe and the B2 intermetallic. The structure tended towards that of alpha-Fe with lower Al contents indicating a decreasing number of Al atoms available to occupy B2 lattice sites. A fine grain size and evidence of tearing indicate that mechanically alloyed Fe-Al intermetallics in the DO3 composition range are ductile at room temperature.