V. Ramakrishna Rao

Effect of carbides on embrittlement of Fe3Al based intermetallic alloys

Iron aluminides based on Fe{sub 3}Al are being considered for high temperature structural applications. These alloys are known to be susceptible to environmental embrittlement in the presence of atmospheric moisture. This embrittlement has been proposed to be due to diffusion of nascent hydrogen liberated by the chemical reaction between aluminium present in the alloy and the atmospheric moisture. The same reaction has also been attributed to induce surface cracking during cutting and machining when a water-based coolant is used. Most of the available literature is on alloys prepared from high purity raw materials containing very low levels of carbon (<0.01 wt.%). Additions of carbon in the range of 0.14 to 0.50 wt.% result in formation of hard (and brittle) Fe{sub 3}AlC precipitates. Here the authors report on the effect of these carbides on the environmental embrittlement of Fe{sub 3}Al.

Effect of carbon content on high temperature tensile properties of Fe3Al based intermetallic alloys

Ordered intermetallic alloys based on the iron aluminide Fe{sub 3}Al are being considered for high temperature structural applications. Though these alloys exhibit poor room temperature ductility and low fracture toughness, significant improvement in these respects can be achieved by alloying addition and process control. Most of the reported literature is on compositions with very low (<0.01 wt.%) carbon contents because carbon is known to embrittle these alloys causing significant reduction in ductility. However, no reasons have been ascribed to this loss in ductility. Recently the authors have reported that addition of carbon in the range of 0.14 to 0.50 wt.% significantly increases the room temperature strength of Fe-16 wt.% (28 at.%)Al alloys. These alloys also exhibited good room temperature by the interstitial carbon, as well as precipitation hardening due to the presence of Fe{sub 3}AlC precipitates. Here, the authors report elevated temperature tensile properties of these alloys.