High strain rate response of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy fabricated by laser additive manufacturing

Under high strain rate loadings, many engineering materials exhibit quite different deformation behavior from those under quasi-static loadings, and adiabatic shear band (ASB) is normally generated with degradation of material property. In this study, the deformation response of LAMed Ti-6.5Al-3.5Mo-1.5Zr-0.3Si titanium alloy (TC11) under high strain rates (2800s⁻¹ and 2900s⁻¹) is investigated for both as-deposited state and heat-treated state (annealed at 1263 K for 1 h followed by annealed at 803 K for 6 h) by using the split Hopkinson pressure bar (SHPB). Results indicate that the as-deposited alloy has a unique mixed grain morphology (coarse columnar grains and fine equiaxed grains) with ultrafine basket-weave microstructure. Under high strain rate loadings, the as-deposited alloy possesses excellent yield strength but with poor plasticity and high adiabatic shear susceptibility. After heat treatment, the yield strength of alloy is sacrificed due to the reduced contents of ultrafine α lamellas, but the partially globularization of continuous grain boundary α phases greatly improves the plasticity of alloy that the adiabatic shear susceptibility is efficiently suppressed.