INFLUENCE OF THERMO HYDROGEN TREATMENT ON HOT DEFORMATION BEHAVIOR AND MICROSTRUCTURAL EVOLUTION OF TI-6AL-4V ALLOY

摘要

The influence of hydrogen on hot deformation behavior and the microstructure evolution of Ti-6Al-4V was investigated. 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. 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. Metallographic study of microstructure evolution after isothermal compression revealed martensite needles and rare and very fine alpha phase grains confirming that the specimens were deformed above the beta transus temperature.