An Evaluation of Microstructure, Texture, and Oxidation Behaviors of Ti-3Al-2.5V

Ti-3Al-2.5V alloy is widely used for tubing and foil applications due to its excellent cold forming characteristics.Ti-3Al-2.5V alloy is an intermediate strength alloy between commercially pure titanium and Ti-6Al-4V. Recently, there are growing trend that could potentially expand the application of Ti-3Al-2.5V in aerospace fastener industry over a wide range of products, from collar to nuts. However, the available fundamental properties and microstructural information for Ti-3Al-2.5V used in aerospace fastener industry is very limited. Thus, over the past few years, Alcoa Fastening System (AFS) conducted a series of evaluations of Ti-3Al-2.5V performance including texture and microstructure relationship to assist the development and applications of new products. 

Air oxidation behavior of a Ti-3Al-2.5V alloy was examined over the temperature range of 1200-1500F for different time intervals. Oxygen diffusion depth and hardness measurements were conducted on the cross-sections of the oxidized alloys to investigate the diffusion coefficient and kinetics. Ti-3Al-2.5V demonstrated higher diffusion coefficient compared to commonly used commercially pure titanium and Ti-6Al-4V. X-ray texture study revealed strong fiber texture with basal plane orientated along radial directions. In addition, Microstructural and mechanical properties relationship of Ti-3Al-2.5V after various heat treatments were also discussed.