Structure and stability of precipitates in 500°C exposed Ti–25V–15Cr–xAl alloys

The effects of thermal exposure on microstructural changes in βTi–25V–15Cr–(2–4)Al alloys (all compositions in wt%) have been investigated. Plasma melted alloys were either HIPped, extruded or forged before being exposed at 550°C for 24–1000h. It was found that αprecipitation occurred in samples of Ti–25V–15Cr–3Al which were exposed at 550°C for 24h. The amount of precipitation increased with exposure time and the composition of the αphase changed gradually. EDX analysis on TEM samples showed increasing Al and Ti and decreasing V and Cr in the precipitates with exposure time. In samples which were exposed at 550°C for over 100h α2was observed. The variation of Al from 2 to 4wt% increased the precipitation and the kinetics of αto α2ordering. The results are discussed in terms of the effects of Al and oxygen on α2precipitation in βTiVCrAl alloys.