Highly oxidation-resistant Ti-Mo alloy with two-scale network Ti5Si3 reinforcement.

• Ti 5 Si 3 with two-scale network architecture was introduced into Ti-4Mo composite. • The composite displays superior oxidation resistance up to 800 °C. • A multi-component surface layer in-situ formed during oxidation. • The adhesion performance of the oxide layer was investigated. • The formation and protection mechanisms of the oxide layer were investigated. There is keen interest in using Ti alloys as lightweight structural materials for aerospace and automotive industries. However, a long-standing problem for these materials is their poor oxidation resistance. Herein, we designed and fabricated a Ti 5 Si 3 reinforced Ti-4(wt.%)Mo composite with two-scale network architecture by low energy milling and spark plasma sintering. It displays superior oxidation resistance at 800 °C owing to the in-situ formation of a multi-component surface layer. This oxide layer has a dense grain size gradient structure that consists of an outer TiO 2 layer and an inner SiO 2 -padding-TiO 2 layer, which has remarkable oxidation resistance and thermal stability. Furthermore, it was revealed that the hitherto unknown interaction between Ti 5 Si 3 reinforcement and nitrogen during oxidation would contribute to the formation of a TiN nano-twin interface layer, which accommodates the thermal mismatch strain between the oxide layer and matrix. This, along with high adhesion, confers excellent thermal cycling life with no cracking or spallation during long-term oxidation. In this regard, the secure operating temperature of this new composite can be increased to 800 °C, which provides a design pathway for a new family of Ti matrix composites for high-temperature applications. [Display omitted] [ABSTRACT FROM AUTHOR]