On the parameters affecting the formation of iron aluminides during pressure-assisted infiltration of aluminium into a preform of steel fibres

The parameters affecting the formation of iron aluminides during reactive i nfiltration of iron-based fibre preforms in a squeeze-casting equipment wer e investigated. The volume fraction of intermetallic phases was found to in crease when the fibre volume fraction and size decreased. The increase of t he temperatures of the die, aluminium and preform allowed avoiding prematur e checking of the plt forms, reducing the gradient of reaction and increasi ng the extent of exothermic reactions. As-infiltrated material with overall chemical composition corresponding to Fe3Al was studied by SEM, X-ray diff raction and TEM. The unreacted iron fibres were surrounded by iron-rich FeA l phases. The single-phase grains adjacent to the boundary layer were ident ified as Fe2Al5 whereas the grains with lamellar morphology were identified as consisting of a mixture of FeAl and FeAl2 lamellae. Heat treatment of s uch an as-infiltrated material resulted in the formation of a fine-grained structure composed of FeAl and Fe3Al phases. (C) 2000 Elsevier Science Ltd. All rights reserved.