Abstract
Abstract The eutectic alloy Al 3 (Nb,Cr) + Cr(Al,Nb) forms an in situ composite and the Al 3 Nb presents high specific strength and low oxidation rate that may be improved by the combination with other phases. The purpose of this work is to investigate physical, mechanical and oxidation properties of the eutectic alloy. Therefore, Rietveld analysis was carried out for furnace cooled and water quenched samples and oxidation tests were performed on directional solidified samples. Compressive tests were performed for the eutectic alloy and also for the Nb–74.8% Cr–24.6% Al alloy in the as-cast condition. The alloy presents 12.9% Cr(Al,Nb) at room temperature, retained from the transformation Cr(Al,Nb) to Al(Nb)Cr 2 . The combination of Al 3 Nb with Cr(Al,Nb) and Al(Nb)Cr 2 considerably improves mechanical behaviour, leading the yield strength to 1525 MPa at 800 °C and 925 MPa at 900 °C. The oxidation tests showed the formation of several oxides at all temperatures studied and that from 900 °C on alfa Al 2 O 3 is formed both in air and O 2 except under O 2 at 1000 °C. It is believed that the Cr(Al,Nb) phase acts as an Al reservoir for the formation of the various Al 2 O 3 scales.
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