Modern superplastic deformation theory that grain boundary sliding is the titanium alloy pump main way of superplastic deformation

Modern superplastic deformation theory that grain boundary sliding is the main way of superplastic deformation, diffusion and dislocation motion inside the grain and the grain boundary is the main coordinating mechanism of grain boundary sliding. Superplastic forming of titanium alloy pump  B-phase diffusion creep or dislocation creep dominated: A phase to the grain boundary sliding-based, coordinated jointly by diffusion and bit dislocation motion; A and B are two phases flow to A and B phase boundary migration to complete. Hydrogen in the titanium alloy superplastic forming :( mainly plays a role in the following) was added to increase the Titanium precision castings diffusivity of hydrogen in the alloy elements, resulting in enhanced B-phase diffusion slip A creep and intergranular phase. (2) the diffusion of hydrogen activated dislocation pinning promote the climb and slide dislocations, improved sliding capacity of B grains, the coordinating role of dislocations in favor of A / A grain boundary sliding requested. (3) hydrogen-induced weak bond effect, reducing the diffusion activation energy, enhanced atomic diffusion capacity, titanium casting process improve the superplastic flow capacity. (4) the addition of hydrogen significantly reduces B \ A + B transition temperature, increase the volume fraction of the B phase, a direct result of the increase and decrease the flow stress of the plastic, so that the titanium alloy can be deformed at a lower temperature and higher deformation rates were superplastic forming.