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

A composition- and temperature-dependent mobility database including bulk, grain boundary and dislocation diffusion in alpha-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 alpha-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.