Implementation of miniature tensile specimens in mechanical properties assessment of directed energy deposited Ti-6Al-4V: As-built and heat treated

Abstract

Within the last two decades, additive manufacturing (AM), a. k.a. 3D printing, has provided promising solutions for producing near-net-shape components with intricate geometries. From the material perspective, titanium alloys, one of humankind's most essential structural materials, are being considered the first candidate for AMed parts due to their unique characteristics in strength-weight-corrosion combinations. However, measuring the mechanical properties of designed geometry remains a challenge due to the ineffectiveness of conventional standard tensile specimens in assessing the site-specific and intricate geometries. In AM, the current approach often consists of evaluating standard-sized samples with the assumption that components with complex geometries possess comparable mechanical properties, even though they may have undergone different thermal processes in various situations. Hence, combining the microstructural characterization, this study aims to investigate the mechanical properties of direct energy deposition (DED) Ti-6Al-4V through a newly designed miniature tensile test (M-TT) specimen. The as-built specimen showed ultimate tensile strength (UTS) of ∼1305.3 MPa and elongation of ∼8.6 % with the mixed basketweave and α-colony microstructure. However, the DED Ti-6Al-4V specimen heat-treated at 850 °C exhibited the highest average elongation of ∼13.2 % and decent UTS of ∼1240.3 MPa with the α+β microstructure.