Understanding the evolution of oxidation in Ti alloys
under high-temperature conditions is crucial for enhancing the long-term
service stability of engineered components. In this study, the high-temperature
oxidation behaviour and kinetics (1000‒1200 °C) of Ti‒14Cu alloys were
investigated, and the evolution of microstructural stress on the alloy surface and
the oxidation mechanism were clarified. The results demonstrated that the oxide
layers on the alloy surface gradually evolved into a multi-layer structure with
increasing temperature. After
oxidation treatment for 5 hours, the oxidation rate increased from 3.50 × 10-3 mg2/(cm4·h) at 1000 °C to 4.17 × 10-2 mg2/(cm4·h)
at 1200 °C. The significant residual stress generated by the difference in the
thermal expansion coefficient of TiO2 and that of the α-Ti matrix
induced rapid crack initiation and propagation in the oxide layer. These cracks
act as rapid diffusion pathways for oxygen, thereby accelerating the oxidation
rate of the Ti–14Cu alloy. Consequently, the dominant factor governing oxidation
shifted from elemental diffusion to interfacial reactions. Molecular dynamics
simulations revealed that tensile stress was concentrated within the oxide layer,
whereas a combination of tensile and compressive stresses developed at the
matrix/oxide layer interface. A large number of semi-coherent interfaces were
formed between TiO2 and the α-Ti matrix during
high-temperature oxidation, leading to enhanced structural disorder and
elevated atomic potential at the matrix/oxide layer interface. Furthermore, a
thin and dense Cu-rich layer formed on the inner side of the oxide layer after
oxidative treatment at 1200 °C, effectively suppressing oxygen diffusion and
inhibiting crack propagation.
