Radial gradient design enabling additively manufactured low-modulus gyroid tantalum structures

Abstract

This work proposes a radial graded porosity design for the fabrication of low-modulus gyroid porous tantalum structures via laser powder bed fusion (LPBF) additive manufacturing, utilizing a combination of simulation and experimentation to investigate its influence on mechanical properties and permeability compared to uniform porous structures. The results demonstrate the excellent printability of the gyroid porous tantalum structures, with the porosity deviation ranging from 0.02% to 2.75%. The elastic modulus of the porous structures ranges from 603.6 MPa to 1317.36 MPa, which is as low as that of human cancellous bones. Structures with radial graded design exhibit a similar deformation behavior as the uniform porous structures. However, due to the edge strengthening, the graded porous structures show increased elastic modulus and yield strength by 2.29–13.94% and 0.03–33% respectively, compared to their uniform counterparts. The enhancement in elastic modulus is more significant for the graded porous structures with the porosity lower than 70%, due to the defects caused by longer overhang lengths in areas of higher porosity. The permeability of the porous structures ranged from 4.324 × 10−9 m2 to 9.648 × 10−9 m2 and increased proportionally with porosity, all falling within the range of cancellous bone permeability. The gradient design exhibits a 2% increase in permeability with a porosity of 59.5%, facilitating nutrient transportation and cell migration. Meanwhile, the radial graded design features a larger surface area with higher wall shear stress, which activates cell growth factors and induces stress fiber formation. These findings offer a promising approach to achieving optimal biological performance and a well-matched elastic modulus with bones through LPBF.