Influence of thermo hydrogen treatment on hot deformation behaviour and microstructural evolution of Ti-6Al-4V alloy

Purpose: The present work compares the hot deformation behaviour at 800°C and microstructure evolution after the isothermal compression test of hydrogen containing specimens with that of non-hydrogenated Ti-6Al-4V alloy. Design/methodology/approach: Specimens in hydrogenated and non-hydrogenated state were tested by means of isothermal compression at 800°C and strain rate of 0.005 s-1 on a Gleeble-3800 machine. Thermal hydrogen treatment of specimens in flowing hydrogen consisted of annealing 1 h at 600°C, 0.5 h at 850°C and aging 4 h at 590°C. Findings: Hydrogen contents in specimens at conditions as-received, heat treated in argon and in hydrogen and after isothermal compression test were measured using an analyzer LECO RH600. Thermal hydrogen treatment resulted in amount of hydrogen as high as 0.98 wt. %. After isothermal compression test the hydrogen content of 0.46 wt. % was retained in the specimens. Practical implications: The THT technology allows improving of fatigue and strength properties through microstructure refinement. Reversible hydrogen alloying provides decreasing flow stress and increasing hot workability of titanium alloys at lowers temperatures. Originality/value: The special heat treatment technology of Ti-based alloys, so-called the thermo hydrogen treatment (THT), employs the reversible reaction of hydrogen with titanium in order to modify phase compositions, evolution of metastable phases and kinetics of phase transformations in titanium alloys.