Development and characterization of minimal surface tantalum scaffold with high strength and superior fatigue resistance

Abstract

Additively manufactured tantalum scaffolds show great promise for load-bearing bone reconstruction due to their exceptional osseointegration and bone in-growth capabilities. Nonetheless, enhancing their mechanical properties, particularly fatigue resistance, remains a critical goal. This study highlights the remarkable mechanical properties of additively manufactured triple periodic minimal surface (TPMS) porous tantalum scaffolds. With a porosity of 70 %, the TPMS tantalum scaffold exhibits a compressive yield strength of 57.6 MPa, surpassing trabecular porous structures with identical porosity by over 70 % and the rhombic dodecahedron (RDOD) structure by over 30 %. Furthermore, its elastic modulus reaches 7.3 GPa, marking a 95 % increase compared to RDOD and trabecular tantalum scaffolds. Notably, this scaffold demonstrates impressive ductility, with no macroscopic brittle fractures even at a maximum strain of 50 %. During static compression, the tantalum scaffold structure showcases a layer-by-layer deformation failure mechanism, leading to a substantial rise in dislocation density and low-angle grain boundaries within the grain regions. This suggests that the failure mechanism primarily arises from plastic deformation and ductile fracture in tantalum materials. The TPMS tantalum scaffold displays excellent fatigue resistance without mechanical fracture failure, maintaining its residual compression yield strength post-testing, unlike the RDOD tantalum scaffold which experiences fatigue failure with a strength of 26 MPa. The TPMS porous structure exhibits superior stress distribution and reduced stress concentration compared to the RDOD design, resulting in enhanced mechanical performances. Given its exceptional mechanical properties, the TPMS tantalum scaffold holds significant potential for clinical applications as load-bearing bone implants.