Influence of Different Heat Exposure Temperatures on the Oxidation,Microstructure, and Room-temperature Tensile Properties ofTi-22Al-25Nb Alloy

Author of the article:ZHAO Xiaobin1, JIA Runchen1, TAN Haibing2, ZENG Weidong1

Author's Workplace：1. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China; 2. SichuanGas Turbine Research Institute of AECC, Chengdu 610400, China

Key Words：Ti2AlNb alloy; high-temperature exposure; microstructure; mechanical properties

Abstract：Ti-22Al-25Nb alloys are recognized as pioneering high-temperature lightweight structural materials characterizedby their exceptional combination of high specific strength and excellent creep resistance, thereby presenting broadapplication prospects in the aerospace field. However, the decline in oxidation resistance at temperatures exceeding 750 ℃limits its development and application. To elucidate the coupling effects of high-temperature thermal exposure on thestructural stability and mechanical properties of the alloy, Ti-22Al-25Nb annular components were subjected to thermalexposure at 700, 750 and 800 ℃ . By integrating room-temperature tensile tests and microhardness experiments withmultiscale microscopic characterization (SEM, TEM), the evolution of the surface oxide layer and oxygen-rich layer, themorphological transformation of the fine plate-like O phase, and their impact mechanisms on the room-temperature strengthand plasticity were analysed. The results indicate that with increasing thermal exposure temperature, the oxide layer andoxygen-rich layer progressively thicken, forming a continuous brittle surface layer with reduced compactness. Concurrently,the thickness of the fine plate-like O phase increases as the aspect ratio decreases, leading to a diminished hindrance effectand a reduction in yield strength. The formation of the brittle surface layer causes cracks to reach critical sizes at an earlystage, resulting in simultaneous degradation of the room-temperature strength and plasticity