Quasi-static and fatigue properties of graded Ti–6Al–4V lattices produced by Laser Powder Bed Fusion (LPBF)

Abstract The additive manufacturing of metallic lattices based on triply periodic minimal surfaces (TPMS) has recently received plenty of interest in the field of hard tissue engineering. Although these structures are deemed to present advantages over conventional designs in regard to their biological and compressive mechanical properties, their fatigue life has received little attention. In the following work, Ti–6Al–4V lattices based on gyroid, diamond and Schwartz primitive unit-cells were tested in quasi-static tension and tension-tension cyclic fatigue. Their resulting elastic and fatigue properties are reported and compared in the context of biomedical applications. Compared to the two others, the Schwartz lattices were found to have the lowest strength for a similar relative density. The Young’s moduli of the three samples however, were of similar magnitude. Basquin’s functions are presented to fit the fatigue S–N curves and these can assist with the fatigue design of lattices with identical unit-cells. Fractography analysis from scanning electron microscopy images revealed that the fatigue crack initiation always occurs at the surface, pointing out the importance of surface treatment in SLM-produced titanium lattices.