Microstructure and mechanical properties of Titanium grade 23 produced by selective laser melting

Abstract

Selective laser melted Titanium grade 23 was characterized by low porosity, relatively large surface roughness and pronounced surface texture (i.e. surface grooves orientation). The band/layer microstructure was built of mixed α and β phases. The as printed structure exhibited very high compressive residual stresses with strong anisotropy (i.e., − 512 ± 17 MPa and − 282 ± 14 MPa along the laser scanning direction and along the transverse direction, respectively) and strong fiber crystallographic texture. The latter one is responsible for the anisotropy of hardness in the material. Annealing at 600 °C during four hours significantly removed residual stresses (i.e. to − 14 ± 2.8 MPa) and slightly weakened the texture. Yield strength, 1120 ± 50 MPa, and ultimate tensile strength, 1210 ± 50 MPa, of the annealed material are significantly higher and tensile elongation, 3.9%, lower than for commercial Titanium grade 23. Final mechanical polishing to obtain flat and relatively smooth surface induced desired compression residual stress in the subsurface (i.e., equal to about − 90 MPa). Low absorbed gas contents (oxygen, nitrogen, hydrogen) and low porosity of the printed material indicates the correctness of the technology and allows the printed material to be classified as meeting the requirements of ASTM standards for Titanium grade 23. Besides traditional testing techniques, the optical profilometry, X-ray analysis (texture and residual stresses measurement) and infrared absorption method were applied for the product characterization and some potential of these testing methods and usefulness in technological practice was discussed, what can be particularly interesting both to practitioners from industry and researches from scientific laboratories.

Microstructural development during additive manufacturing of biomedical grade Ti-6Al-4V alloy by three-dimensional binder jetting: material aspects and mechanical properties

“…Therefore, for the additive manufacturing of titanium, environmental control at different processing stages (powder handling, storage, 3D printing, de-binding, and sintering) is of critical requirement. Here, it is essential to mention that the amount of oxygen content in the specimens prepared by binder jetting is comparable with those made by selective laser melting (about 3000 ppm) [33]. Kazantseva et al [34] have shown that on the laser printed surface, the amount of oxygen and nitrogen can reach 3 wt.% and 0.05 wt.%, respectively.…”

“…The interstitials entrapped in the metal are responsible for increased tensile strength and reduced elongation. In contrast to annealed specimens after selective laser melting with a tensile strength of 1210 ± 50 MPa and tensile elongation of 3.9% [33], the mechanical properties of parts manufactured by binder jetting are closer to the commercial titanium alloy.…”

Microstructural development during additive manufacturing of biomedical grade Ti-6Al-4V alloy by three-dimensional binder jetting: Materials aspects and mechanical properties

“…Therefore, for the additive manufacturing of titanium, environmental control at different processing stages (powder handling, storage, 3D printing, de-binding, and sintering) is of critical requirement. Here, it is essential to mention that the amount of oxygen content in the specimens prepared by binder jetting is comparable with those made by selective laser melting (about 3000 ppm) [33]. Kazantseva et al [34] have shown that on the laser printed surface, the amount of oxygen and nitrogen can reach 3 wt.% and 0.05 wt.%, respectively.…”

Surface Characteristics and Residual Stress Variation in Semi-Deep Hole Machining of Ti6Al4V ELI with Low-Frequency Vibration-Assisted Drilling

“…These distinctive attributes have rendered titanium highly coveted in various high-value sectors, notably in aerospace and related industries [3]. Within this class of alloys, Ti-6Al-4V extra low interstitial (ELI) stands out for its notable suppression of impurities, resulting in enhanced ductility and fracture toughness compared with the conventional Ti-6Al-4V [4,5]. Notably, it maintains resilience even at extremely low temperatures, rendering it indispensable in cryogenic applications.…”