On the properties of the eutectic alloy Al3(Nb,Cr)Â +Â Cr(Al,Nb)

The eutectic alloy Al3(Nb,Cr) + Cr(Al,Nb) forms an in situ composite and the Al3Nb 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)Cr2. The combination of Al3Nb with Cr(Al,Nb) and Al(Nb)Cr2 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 Al2O3 is formed both in air and O2 except under O2 at 1000 °C. It is believed that the Cr(Al,Nb) phase acts as an Al reservoir for the formation of the various Al2O3 scales.