Influence of hydrogen on tensile property of Ti-6AI-4V

The influence of hydrogen content on the microstructure and the tensile property of Ti-6Al-4V alloy was studied, and the phenomenon of minimum yield stress at certain hydrogen content was discussed. The results show that Ti-6Al-4V alloy can absorb hydrogen above 600°C and the different hydrogen contents can be achieved by changing the flow rate of hydrogen. With increase of hydrogen contents, the microstructure gradually transforms from the original near basket-type to the a clusters which consist of opiates and hydrides distributed in α plates, and then to the mixture of α, βand the large amount of hydrides. When the specimens tensioned at 600°C, their strength first decreases and then increases, but their ductility changes quite the contrary as increasing hydrogen contents. There is optimum hydrogen content at which the strength is the lowest and the plasticity is the highest for the specimens tensioned at 600°C. Ti-6Al-4V alloy may gain the higher tensile strength or better ductility at 600°C through appropriate hydrogenation treatment in comparison with samples untreated. With increase of hydrogen contents, the fracture type transforms from microvoid coalescence type to "cleavage like" type for specimens tensioned at 600°C.