Evolution of microstructure and mechanical properties of Ti-5Mo-5Al-5V alloy processed by high pressure deformation

The evolution of Ti-5Mo-5Al-5V alloy microstructures after severe plastic deformation (SPD) by high pressure hydrostatic extrusion has been studied by electron and optical microscopy, and X-ray analysis. It has been established that the deformation mechanism depends on the phase composition of the alloy. The monophase 100% beta-state is deformed by formation of deformation package martensite which contains disoriented fragments having sizes of about 20 nm. At early stages of deformation, a translation mechanism is observed in the two-phase alloy. At severe deformations this mechanism changes into a bending one. Reorganization of structure during the aging heat treatment of the as-deformed alloy causes an increase of the alloy strength by 35-40% while maintaining plasticity.