Fractography, Fracture Toughness and Structural Turbulence Under Low-Temperature Shock Loading of a Nonequilibrium Titanium Alloy Ti–6Al–4V

The titanium alloy Ti–6Al–4V with strongly nonequilibrium α- and β-phases has been studied for the first time. For this, it was subjected to cross-helical rolling (CHR) at T = 1000°C (above the polymorphic transformation temperature), and then quenched in water in order to partially preserve vanadium in the α-phase, and aluminum in the β-phase. Under active uniaxial tension, the non-equilibrium VT6 alloy was deformed in the absence of strain hardening at room temperature. Alloys treated with CHR below the polymorphic transformation temperature showed traditional parabolic hardening. The non-equilibrium of the VT6 alloy caused a strong increase in its impact toughness at low temperatures down to T = –70°C. The fatigue life of a nonequilibrium alloy has doubled. If the initial alloy has ductile-brittle fracture at low negative temperatures, then the nonequilibrium alloy deforms viscously with all signs of structural turbulence. Structural turbulence in a nonequilibrium alloy manifests itself in the temperature range from 20 to –70°C, during deformation of 3D-printed samples, under conditions of shock separation of diffusion-sintered multilayer VT6 alloy packets.