Effect of hydrogen content on superplastic forming/diffusion bonding of TC21 alloys

The superplastic forming and diffusion bonding (SPF/DB) of hydrogenated TC21 alloys was carried out in the temperature range of 1073–1193 K under 1.5 MPa gas pressure. The effects of hydrogen contents on bonding ratio of SPF/DB and microstructure of interface and substrate for TC21 alloys were investigated by OM, SEM and TG–DTA. The experimental results showed that bonding ratio of SPF/DB increased with the increase of hydrogen contents. However, it decreased at hydrogenated 0.5 wt%. With the same hydrogen content, bonding ratio increased with the increase of temperature. The size and amounts of voids distributed along the interface decreased with the increase of hydrogen contents, and the recrystallization of joint grains through the interface was formed.