Effect of carbon content on mechanical properties of electroslag remelted Fe3Al based intermetallic alloys

The effect of carbon content (0.013 to 0.50 wt% C) on structure and mechanical properties of electroslag remelted iron aluminides based on Fe3Al containing approximately 16wt% (28at%) aluminium alloy has been studied. At low carbon contents (0.031 wt% or less) the ESR ingots suffer from hydrogen embrittlement which results in poor mechanical properties. At high (0.074 wt% or more) carbon contents the hardness and strength of ESR ingots increase with increasing carbon content without significant change in ductility. This is attributed to the solid solution strengthening arising from interstitial carbon present in the Fe3Al matrix as well as to the increased amount of Fe3AlC (perovskite) precipitation. The mechanical properties of these high carbon ESR cast alloys are comparable or superior to those reported for high purity wrought alloys with similar aluminium contents. The machinability of ESR ingots improves with increase in carbon content. This is attributed to the presence of uniformly distributed Fe3AlC precipitates in the ingots which allow formation of small and uniform size chips during machining.