Study On Microstructure Evolution And Deformation Properties Of Cyclic Hydrogenated Titanium Alloys

Titanium alloys have lots of advantages, such as a large specific strength, good corrosion resistance, reliable high temperature performance, etc. It has been widely used in the aerospace field. But the low plastic and large deformation resistance in the room temperature restrict the development of its cold forming. Because most of the titanium alloys were formed at a high temperature which highly increase the manufacturing cost and limits the application of titanium alloys. Thermohydrogen processing(THP) uses hydrogen as a temporary alloying elements, it can help to change the hot-working character of titanium alloy with the hydrogen-induced phase transformation, hydrogen-induced plasticity, reversible alloying properties. Thermohydrogen processing research is focused on a single pass of the hydrogenation process, and the research about multi-pass cyclic hydrogenation is still a blank field at home and abroad. In this paper, the microstructure and mechanical properties of multi-pass cyclic hydrogenation of Ti6A14V titanium alloys were investigated systematically by the use of optical microscopy, X-ray diffraction, TG, compression test at room temperature and other means.The effects of different hydrogen contents on wear property of T16A14V alloy were investigated using a M-200 type tribometer. First-principles methods were used to construct different hydrogen concentrations of aTi-H crystal system, aTi-H system structure, energy, band structure, variation of the electron density of states were studied under different hydrogen content.The results showed that:The limt deformation rate of first-pass hydrogenation titanium alloy increased by 17.62%, the increasing content of β phase could improve the room temperature plasticity of titanium alloy. Multi-pass cyclic hydrogenation caused hydrogen embrittlement in titanium alloy and promoted the generation of hydrides in the microstructure of Ti6A14V. With the increasing of hydrogenation passes, the quantity of needle α’ martensite reduced, a" martensite raised.The multi-pass cyclic hydrogenation specimens were compressed at room temperature, which found that the grain was bent and refined to a certain extent, volume fraction of a" martensite increased and the formation of shear zone was not found. The friction coefficient of Ti6A14V alloy decreases after hydrogenation. The effect of hydrogen content on friction coefficient is not apparent. The wear-resistant property of the alloy becomes worse with the increasing of hydrogen content. The oxidative wear of the alloy weakens and abrasive wear enhances with the increasing of hydrogen content.Ti-H unit cell’s volume and volume expansivity rasied with the increasing of the hydrogen content while lattice distortion occurred, cell structure became unstable which accelerated the formation of titanium hydride. The steady-state energy and impurity formation energy decreased with the rasing of hydrogen content.The energy band structure of pure Ti exhibited the typical characteristics of the metallic conductor, while the energy band was around the Fermi level with a intensive distribution.There existed a weak bond effect for the decreasing of hydrogenated titanium atoms bonding force.