Fe/Al2O3 composites with metal contents between 23 and 35 vol% have been fa
bricated via Al-assisted pressureless reaction sintering. The effect of var
iation of oxygen partial pressure during sintering on phase development, mi
crostructure and mechanical properties has been investigated. The formation
of the spinel phase FeO . Al2O3 is found to occur at elevated temperatures
if the oxygen partial pressure during sintering exceeds a critical value.
Microstructural observations and image analysis reveal that the composites
exhibit a microstructure with the ceramic and the metal phase forming inter
penetrating networks. The fracture toughness increases with increasing meta
l content and strongly depends on the phase content of the sintered specime
ns. In composites containing a small amount of FeO . Al2O3, the maximum tou
ghness is 7.1 MPa root m. A significant toughness enhancement up to 10.2 MP
a root m was achieved by avoiding the spinel formation to obtain composites
consisting only of Fe and Al2O3. (C) 1999 Elsevier Science Ltd. All rights
reserved.