The effects of gaseous and liquid environments on the fracture behavio
r of Fe3Al and FeAl are reviewed. The influence of variables such as c
omposition, microstructure, loading rate and temperature are described
. It is shown that the iron aluminides, when tested in dry environment
s (oxygen, dry air, vacuum) are inherently ductile, but that the prese
nce of very small levels of moisture is sufficient to cause severe emb
rittlement. Hydrogen, whether released from water vapor or directly in
contact with the iron aluminides, is the agent of embrittlement. A de
tailed discussion of the mechanism of embrittlement is included. Allev
iation of embrittlement by such techniques as alloying, surface protec
tion and control of microstructure is outlined. Finally, the environme
ntal embrittlement of iron aluminides is contrasted to that of other a
luminides; the major difference is shown to be the propensity for clea
vage fractures in FeAl and Fe3Al, compared to intergranular fracture i
n L1(2) polycrystals.