Fatigue behaviour and biocompatibility of additively manufactured bioactive tantalum graded lattice structures for load-bearing orthopaedic applications.

Laser powder bed fusion (LPBF) additive manufacturing of pure tantalum and their graded lattice structures was systematically investigated, with emphasis on their microstructure evolution, phase formation, surface energy and biological properties in comparison with conventionally forged pure Ta. The LPBF fabricated Ta (LPBF-Ta) exhibited lower contact angles and higher surface energy than the forged-Ta which indicated the better wettability of the LPBF-Ta. The adhesion and proliferation of rat bone marrow stromal cells (rBMSCs) were also enhanced for the LPBF-Ta when compared to forged-Ta. Three different Ta graded gyroid lattice structures (i.e., uniform structure, Y-gradient structure, Z-gradient structure) were designed and fabricated using the same optimised LPBF parameters. Y-gradient structures exhibited the best plateau stress and compressive modulus among three different graded structures due to the maximum local volume fraction on the fracture plane. In fatigue response, Y-gradient outperformed the other two gyroid structures under varying stresses. In terms of cell culture response, the uniform structures performed the best biocompatibility due to its suitable pore size for cell adhesion and growth. This study provides new and in-depth insights into the LPBF additive manufacturing of pure Ta graded lattice structures with desired fatigue and biological properties for load-bearing orthopaedic applications.