氢含量对 Ti65 高温钛合金组织性能及扩散连接质量的影响

The effect of different hydrogen contents on the microstructure and diffusion bonding quality of Ti65 high-temperature titanium alloy was investigted. Microscopic characterization methods such as SEM, OM and EBSD were used to reveal the quantitative relationship between hydrogen content and β phase evolution. The results show that the rolled titanium alloy sheet after hydrogen treatment has a typical gradient structure. Equiaxed α grains are formed in the surface layer (10 μm depth region) due to hydrogen-induced recrystallization, while the core region retains the deformed structure and undergoes β phase enrichment and α′ martensitic transformation. With the increase of hydrogen content from 0% to 0. 5%, the volume fraction of β phase increases from 0. 5% to 18. 5%; when the hydrogen content is less than 0. 3%, the mechanism of hydrogen-promoted β phase nucleation is dominant. During the diffusion bonding process, hydrogen atoms significantly improve the diffusion bonding quality by reducing the interface diffusion activation energy. The shear strength of the sample with 0. 4% hydrogen reaches 573 MPa, which is nearly 7 times higher than that of the hydrogen uncharged sample, and the welding rate increases from 14% to 91%. However, hydrogen content exceeding 0. 5% will induce grain boundary hydrogen embrittlement, leading to the decrease in joint strength. There is a significant positive correlation between β phase content and welding rate, indicating that β phase plays a key role in promoting void closure during diffusion bonding and acting as a rapid atomic diffusion channel. The conclusion shows that the optimal hydrogen content for diffusion bonding of Ti65 high-temperature titanium alloy is 0. 4%.