Laser Powder Bed Fusion Additive Manufacturing of a Low-Modulus Ti–35Nb–7Zr–5Ta Alloy for Orthopedic Applications

Abstract

Laser powder bed fusion (L-PBF) was attempted here to additively manufacture a new generation orthopedic β titanium alloy Ti–35Nb–7Zr–5Ta toward engineering patient-specific implants. Parts were fabricated using four different values of energy density (ED) input ranging from 46.6 to 54.8 J/mm3 through predefined laser beam parameters from prealloyed powders. All the conditions yielded parts of >98.5% of theoretical density. X-ray microcomputed tomography analyses of the fabricated parts revealed minimal imperfections with enhanced densification at a higher ED input. X-ray diffraction analysis indicated a marginally larger d-spacing and tensile residual stress at the highest ED input that is ascribed to the steeper temperature gradients. Cellular to columnar dendritic transformation was observed at the highest ED along with an increase in the size of the solidified features indicating the synergetic effects of the temperature gradient and solidification growth rate. Density measurements indicated ≈99.5% theoretical density achieved for an ED of 50.0 J/mm3. The maximum tensile strength of ≈660 MPa was obtained at an ED of 54.8 J/mm3 through the formation of the columnar dendritic substructure. High ductility ranging from 25 to 30% was observed in all the fabricated parts irrespective of ED. The assessment of cytocompatibility in vitro indicated good attachment and proliferation of osteoblasts on the fabricated samples that were similar to the cell response on commercially pure titanium, confirming the potential of the additively manufactured Ti–35Nb–7Zr–5Ta as a suitable material for biomedical applications. Taken together, these results demonstrate the feasibility of L-PBF of Ti–35Nb–7Zr–5Ta for potentially engineering patient-specific orthopedic implants.

A comprehensive review of Gum metal's potential as a biomedical material

“…The primary mechanism of plastic deformation was grain rotation, primarily due to the elevated number of grain boundaries. 143 Nadammal et al 144 manufactured Ti-23.7Nb-1.74Ta-4.83Zr alloys using the L-PBF method. They prepared the alloys with varying energy densities.…”

“…In all cases, the microstructure of the alloys comprised solely of the β-phase. 144 Table 6 serves as a summary of several noteworthy research endeavors conducted ever since the initial advent of these exceptional alloys. Indeed, the groundbreaking study by Saito et al 19 initially utilized a powder metallurgy approach; Table 6 provides evidence that exploration of alternative processing routes has taken place, especially during the last stage of deformation, innovations have been introduced, such as substituting cold swaging with techniques like cold rolling, HPT, and ECAP etc.…”

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“…The mismatch between the mechanical properties of implant and bone tissue was unsolved. Recently, researchers have begun to focus on new ß titanium alloys ( Nadammal et al, 2022 ; Sing, 2022 ; Vonavkova et al, 2022 ). This material can retain the unstable phase, such as the sub-stable ß phase or martensite structure, at room temperature, giving the material good processing plasticity and toughness.…”

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“…[5][6][7] Most recently, some of these alloys have been processed by additive manufacturing. 8 Despite their promise, they are yet to be widely adopted for manufacturing implants in the clinic. 316L SS continues to be popular in view of its corrosion resistance, cost-effectiveness, ease of manufacturing, and established history as an orthopedic biomaterial.…”