Ductility improvement in iron aluminides

Abstract

Excellent high temperature properties of intermetallic aluminides recommend their use for structural applications in sulphurous atmospheres. Interest was not sustained in them because of their brittleness at ambient temperatures. Fe3Al based alloys (air induction melted) were taken up to study the effect of deviations from stoichiometry (both sub and super), third and fourth alloy additions, B, Ti (micro as well as macro), on physical and mechanical properties (at ambient temperatures). The columnar grains observed in sub and stoichiometric compositions were found to become equiaxed on additions of alloy. The microstructures became finer on hot forging and rolling. The hot workability of these alloys increased from 65 to 85% at 973 K on B, Ti additions. The ultimate tensile strength (UTS) and per cent, elongation E increased to 80 kg mm(-2), 3.0% and 94 kg mm(-2), 5%, respectively, for sub and stoichiometric alloys on B and Ti additions. The superstoichiometric alloys displayed dendritic structure and could not be hot worked due to cracking during forging, even after additions of alloys. The stoichiometric Fe3Al alloy with B and Ti additions exhibited the best properties under the experimental conditions.