Enhanced dynamic compression properties of a low density near-α titanium alloy associated with deformation induced laminated microstructure and dynamic segregation

Excellent dynamic properties are demanded for titanium alloys that operate under shock-loading environments. In this work, we demonstrate that a Ti-8Al-1Mo-1V-0.23C alloy with a low density of 4.36 g/cm³ exhibits superb dynamic compression properties, an excellent dynamic strength of ∼1.72 GPa and a dynamic compressive strain of ∼27.2%, due to the synergic effect associated with deformation induced laminated microstructure and deformation promoted carbon segregation. The low-density Ti-8Al-1Mo-1V-0.23C alloy is composed of nano-ordered Ti₃Al (α₂) particles reinforced equiaxed α phase grains bonded by β phase boundaries. The formation of dual-phase laminated microstructure is attributed to plastic flow stability of α phase grains associated with the geometrical constraint imposed by the relatively hard β phase and the activation of prismatic 〈a〉 and pyramidal 〈c + a〉 dislocations. The heat generated by severe plastic deformation in α phase is dissipated by facilitating carbon segregation along slip traces, thus effectively retarding strain softening associated with dynamic recrystallization. Shear instability is eventually triggered due to plastic deformation incompatibility between α and β phase, resulting in the local rotation of laminated microstructure. Adiabatic shear bands (ASBs) happen in the geometrical shear bands. The severe deformation generated heat promotes dynamic recrystallization and strain softening in the shear bands. Our work offers a strategy for the development of Ti alloys with excellent dynamic response via coupling microstructure engineering and thermodynamic segregation-dissipation mechanisms.