Highly Anti-Oxidized Ti-4Mo Alloy With Two-Scale Network Architectured Ti 5 Si 3 Reinforcement

Titanium alloys are desirable for applications in advanced hypersonic aircraft engines and gas turbines, but currently few materials can satisfy the associated high temperature oxidation requirements. Herein, we designed and fabricated a Ti5Si3 reinforced Ti-4Mo composite with a 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 been revealed to have a dense grain size gradient structure that consists of an outer TiO2 oxide layer and an inner TiO2 and SiO2 mixed oxide layer with a core-shell structure, which has remarkable oxidation resistance and thermal stability. Furthermore, it was revealed that the hitherto unknown interaction between Ti5Si3 reinforcements and nitrogen during oxidation would contribute to the formation of a TiN nano-twin interface layer, which accommodates the thermal mismatch strain between 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 can be increased to 800°C, which can provide a design pathway for a new family of titanium matrix composites for high-temperature applications.