High temperature healing of Ti2AlC: On the origin of inhomogeneous oxide scale

The microstructure of oxide scales formed on Ti2AlC surface after oxidation at 1200 °C is investigated. The results reveal an inhomogeneous morphology of the oxide scales, i.e. islands of coarse rutile grains pile up on fine-grained Al2O3 layer. Local cross-sectional observations show that the rutile islands grow on top of cavities in the parent material. A model is proposed to describe the resulting microstructure after oxidation. These results are relevant in optimizing the self-healing conditions of Ti2AlC at high temperature.

► Inhomogeneous morphology of oxides formed on Ti2AlC surface during high temperature oxidation.
► Initial surface curvature attribute to this non-uniform oxidation behavior.
► A columnar layer of Al2O3 was observed between the matrix and equiaxed grain layer on flat surface.
► The Al-ion consumption in cavity is larger than on flat surface during oxidation.
► Porosity and cavity provide paths for outward diffusion of Ti-ion during oxidation.