Interfacial microstructure evolution mechanism of high temperature oxidation-resistant Al-based coating on Ti alloy surface

The interfacial microstructure of an Al-based coating on a Ti alloy surface has been designed by using phase diagrams and advanced first-principles calculations. Samples were characterized by x-ray diffractometry, scanning electron microscopy, optical microscopy, high resolution transmission electron microscopy and energy-dispersive spectrometry. The results show that the stability sequence of the Ti–Al intermetallics was Ti₃Al > TiAl > TiAl₂ > TiAl₃. The TiAl₃ transition layer with a strong self-healing property was obtained easily by metallurgical reaction of Al and Ti. The Al atoms in TiAl₃ combined rapidly with the O atoms to form a new Al₂O₃ protective layer in air. This work provides theoretical support for the thermal processing of Ti alloys. (paper)