Effect of hydrogen content and stress state on room-temperature mechanical properties of Ti-6Al-4V alloy

This work aims to investigate the effects of hydrogen content (in the range of 0%–0.5%, mass fraction) and stress state (tension and compression) on the room-temperature mechanical properties of Ti-6Al-4V alloy through mechanical properties tests. The effects of hydrogen content on microstructure evolution of Ti-6Al-4V alloy is also examined by optical microscopy, X-ray diffractometry, transmission electron microscopy and scanning electron microscopy. The results show that hydrogen content and stress state have important effects on the room-temperature mechanical properties of Ti-6Al-4V alloy. Tensile strength and ultimate elongation decrease with increasing the hydrogen content, while compressive strength and ultimate reduction are improved after hydrogenation. The reason is that the intergranular deformation dominates at the state of tension. Hydrogen atoms in solid solution and hydrides at grain boundaries increase with increasing the hydrogen content and they can promote the initiation and propagation of cracks along grain boundaries. While the intragranular deformation dominates at the state of compression. The plastic beta phase and hydrides increase with increasing the hydrogen content and they improve the ultimate reduction and compressive strength.