Evolution of the structural and phase states of a Ti-6Al-4V alloy in forming submicrocrystalline structure with the use of temporary hydrogenation

The special features of the evolution of the structural and phase states of a Ti-6Al-4V alloy in forming submicrocrystalline structure with the use of temporary hydrogen treatment are studied by electron microscopy and x-ray diffraction analysis. Plastic deformation in the α + β two-phase region at 1023 K is found to initiate a complete β → α transformation in a Ti-6Al-4V-H alloy to form an α phase with lattice parameters different from those of the equilibrium α phase. Isothermal annealing at a dehydrogenation temperature of 873 K gives rise to α + β two-phase submicrocrystalline structure with a grain size of ∼ 0.3 μm. The use of nonequilibrium hydrogen release in the deformed Ti-6Al-4V-H alloy exposed to electron beams is shown to result in one-phase submicrocrystalline structure and grain refining. Possible reasons underlying the phase transformations in the alloy under study are discussed. © 2006 Springer Science+Business Media, Inc.