Isothermal Oxidation Behavior of Ti-Si Eutectic Alloys with Al and Nb Addition

Abstract

Abstract The oxidation behavior of Ti-Si eutectic alloys with various Al and Nb contents was investigated at 850°C in atmosphere. The oxide layer of various oxidation time were examined using scanning electron microscopy (SEM) equipped with an energy-dispersive x-ray analysis (EDX), x-ray powder diffraction (XRD), with the aid of optical microscopy (OM) techniques. The oxidation kinetics follows a parabolic rate law. The oxidation rate decreases gradually as the oxidation proceeds. The results of oxidation kinetics and oxide scales formed in the test temperature indicate that addition of 4.9 wt% Al and 8 wt% Nb imparts excellent oxidation resistance, while a higher Al content (6.9 wt%) and Nb (8 wt%) result in worse oxidation resistance. In all the alloys, the scale was composed of a layer of coarse grain titanium dioxide (TiO2, rutile), alumina (Al2O3), and silicon dioxide (SiO2), which mixed with each other to form a compact and strongly cohesive substrate for the further growth of oxide scale. Correct ...