Microstructure evolution and tensile properties of Ti–6.5Al–2Zr–Mo–V alloy processed with thermo hydrogen treatment

In the current work, Ti–6.5Al–2Zr–Mo–V alloy is processed with hydrogenation, solution-aging and dehydrogenation, that is, thermo hydrogen treatment (THT). Microstructure evolution and phase transformation during THT are investigated. Results show that after aging the microstructure consists of primary α needle, fine acicular eutectoid product and undecomposed βH. At the end of dehydrogenation, the microstructure is composed of fine, fragmented β pieces. Recrystal α grain also occurs in some of the dehydrogenated samples. The fragmented β pieces form by phase transformation βH→α+β+H ↑, and the recrystallization occurs via δ→α+H ↑. Tensile results show that the strength of Ti–6.5Al–2Zr–Mo–V alloy after THT increases remarkably, which is about 30% higher than that of the as-cast alloy.