Structural Evolution and Mechanical Properties of a VT22 Titanium Alloy Under High-Temperature Deformation

Resumo

The special features inherent in the development of high-temperature deformation and structural evolution in materials are investigated, using a VT22 titanium alloy of the transition class (Ti – 4.74 mass% Al – 5.57 mass% Mo – 5.04 mass% V) subjected to helical rolling + aging as an example. This treatment is found to give rise to an intragrain fine acicular martensite structure with fine inclusions of α-phase particles of size ~1 μm. It is shown that in the alloy undergoing plastic deformation at temperatures approaching the polymorphic transformation temperature, the elongation to failure is in excess of 300%. The high plasticity of the alloy in the conditions considered is likely to be due to vigorous development of phase transformations and intensification of diffusion-controlled processes, including the effects of the evolution of the dislocation structure, growth of subgrains, and formation of new grains in the bulk of the pre-existing ones during plastic deformation.