Effect of alloying on aqueous corrosion and mechanical behaviour of iron aluminide Fe3AI

Passivity-inducing elements have been added to iron aluminide, FeaAI, 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 FeaAI-5M (M =Cr, Me, Ta and Ti) was superior compared to that of binary FeaAI 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. FeaAI-5M1 (M1 = Me, Ta, V, Nb and Si) intermetallics could not be processed thermomechanically at 1000 ~ because they cracked during deformation processing. The Fe3AI-5Cr and Fe3AI-5Ti intermetallics could be processed up to 80 % deformation at 1000 ~ 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. 1