In situ study of phase transformations in Ti-6Al-4V-xH alloys

The hydrogen-induced microstructure evolution and phase transformations in Ti-6Al-4V alloy during heating and cooling were studied. The specimens were heated to 1273 K and subsequently cooled to room temperature. The hydrogen content is up to 0.8% (mass fraction). The hydrogen-induced dynamic phase transformations and the corresponding mechanisms were analyzed. When the hydrogen content increases, the β transus temperature significantly decreases and the magnitude decreases, and the volume fraction of β phase increases. During heating, the phase transformations in hydrogenated Ti-6Al-4V alloys can be divided into three stages, and the phase transformation order is δ→α+H2↑⇒δ+α'→βH⇒α'→αH+βH⇒αH→α+H2↑⇒α→β⇒βH→β+H2↑. In addition, the relationship among hydrogenation and Ms and Mf of α' martensite were determined.