Effect of alloying on aqueous corrosion and mechanical behaviour of iron aluminide Fe3Al

Passivity-inducing elements have been added to iron aluminide, Fe3Al, to tackle their poor room-temperature ductility problem. The effect of alloying on the aqueous corrosion and mechanical behaviour of iron aluminides has been examined. It was found that the corrosion behaviour of intermetallic Fe3Al-5M (M = Cr, Mo, Ta and Ti) was superior compared to that of binary Fe3Al in electrolytes of pH 4 (H2SO4) and pH 8 (NaOH). The relative corrosion behaviour of these intermetallics in these electrolytes was comparable. The possible reasons for passivity enhancement have been discussed. Fe3Al-5M(1) (M(1) = Mo, Ta, V, Nb and Si) intermetallics could not be processed thermomechanically at 1000 degrees C because they cracked during deformation processing. The Fe3Al-5Cr and Fe3Al-5Ti intermetallics could be processed up to 80% deformation at 1000 degrees C by rolling into thin strips. These intermetallics exhibited improved room-temperature ductilities but poor yield strengths. The improvement in ductility has been attributed to passivity and microstructural effects. The low yield strengths of these intermetallics are poorly understood.