Highly oxidation-resistant Ti-Mo alloy with two-scale network Ti_(5)Si_(3)reinforcement

摘要

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.