High-temperature oxidation of pure Al: Kinetic modeling supported by experimental characterization

Highlights: • Reliable diffusion mobility database in α-Al₂O₃ phase was developed. • Experimental measurements on aluminum exposed at 1350 °C in air for 24 h were made. • Quantitative kinetic modeling of high-temperature oxidation were performed. • One parameter set of alum inum diffusion can reproduce all the experimental data. • External and internal oxidation occur simultaneously during oxidation of Al. - Abstract: A composition- and temperature-dependent mobility database including bulk, grain boundary and dislocation diffusion in α-Al₂O₃ was developed. Three sets of mobility parameters for aluminum diffusion were evaluated. The experimental results including mass gain, oxide scale microstructure resulting from aluminum exposed at 1623 K under PO₂ = 0.21 bar for 24 h were presented. Kinetic modeling of oxidation of pure aluminum were performed using CALPHAD method. The parameter set supporting that aluminum diffusion in α-Al₂O₃ has similar order of magnitude with oxygen diffusion can reproduce the experimental oxide thicknesses with good accuracy. Both simulations and experiments indicate internal and external oxidation occur simultaneously.