Effect of carbon and processing on structure and mechanical properities of Fe-11 wt.% Al alloy

Ingots of Fe–Al alloys containing 11 wt.% Al and 0.5 and 1.1 wt.% C were prepared by a combination of air induction melting with flux cover (AIM) and electroslag remelting (ESR). The ESR ingots were hot forged at 1373 K to 53% reduction and subsequently hot rolled at 1373 K to 53% rolling reduction. The cast ESR samples were placed in a hearth furnace at 873, 1073 and 1273 K for 24 h then furnace cooled to room temperature. The Fe-11 wt.% Al alloy containing 1.1 wt.% C exhibited a significant higher yield strength at test temperature up to 773 K than alloy containing 0.5 wt.% C. This may be attributed to the presence of large amount of hard Fe3AlC0.5 precipitates in the alloy. The thermo-mechanical processing of cast ESR ingots has resulted in significant improvement in room temperature tensile ductility. This may be due to breaking of cast dendritic structure and more uniform distribution of Fe3AlC0.5 precipitates. These high carbon Fe-11 wt.% Al alloys exhibited excellent resistance to decarburization up to 1273 K because of the formation of continuous protective Al2O3 film on the surface. It would appear from the present work that thermo-mechanically processed high (1.1 wt.%) carbon ESR alloy exhibit an attractive combination of properties.