Hydrogen Treatment Technology For Titanium And Titanium Alloys

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At present, there are two ways to use hydrogen treatment technology to improve the superplastic properties of titanium alloys:

1. Using the plasticity effect of hydrogen, an appropriate amount of hydrogen is added before the superplastic forming of titanium alloy to increase the proportion of B phase in titanium alloy, reduce the flow stress during superplastic deformation, and achieve the purpose of improving the superplastic performance of titanium alloy.
2. The microstructure of titanium alloy was refined by hydrogen treatment, and ultra-fine crystalline titanium alloy was prepared by combining plastic deformation technology, so that the titanium alloy had excellent superplastic properties at lower deformation temperature and higher deformation rate.

According to the modern theory of superplastic deformation, grain boundary slip is the main mode of superplastic deformation, and diffusion and dislocation movement within grain grains and grain boundaries are the main coordination mechanisms of grain boundary slip. In the superplastic forming of titanium alloys, phase B is dominated by diffusion creep or dislocation creep: phase A is dominated by grain boundary slip, which is coordinated by diffusion and dislocation motion; The flow between phases A and B is accomplished by the migration of phases A and B. Hydrogen mainly plays the following roles in the superplastic forming of titanium alloys:

1. The addition of hydrogen improves the diffusion ability of alloying elements, resulting in the enhancement of diffusion creep of phase B and intergranular slip of phase A.
2. The diffusion of hydrogen activates the pinning dislocation, promotes the climbing and sliding of the dislocation, improves the sliding ability of B grains, and is conducive to the dislocation coordination required by the sliding of A/A grain boundaries.
3. The weak bonding effect of hydrogen reduces the diffusion activation energy, enhances the atomic diffusion ability, and improves the superplastic flow ability.
4. It can be seen from the Ti2H phase diagram that the addition of hydrogen significantly reduces the BA+B transition temperature and increases the volume fraction of B phase, which directly leads to the improvement of plasticity and the reduction of flow stress, so that the titanium alloy can be superplastically formed at a lower deformation temperature and a higher deformation rate.