Rationally designed functionally graded porous Ti6Al4V scaffolds with high strength and toughness built via selective laser melting for load-bearing orthopedic applications

Functionally graded materials (FGMs) with porosity variation strategy mimicking natural bone are potential high-performance biomaterials for orthopedic implants. The architecture of FGM scaffold is critical to gain the favorable combination of mechanical and biological properties for osseointegration. In this study, four types of FGM scaffolds with different structures were prepared by selective laser melting (SLM) with Ti6Al4V as building material. All the scaffolds were hollow cylinders with different three-dimensional architectures and had gradient porosity resembling the graded-porous structure of human bone. Two unit cells (diamond and honeycomb-like unit cells) were used to construct the cellular structures. Solid support structures were embedded into the cellular structures to improve their mechanical performances. The physical characteristics, mechanical properties, and deformation behaviors of the scaffolds were compared systematically. All the as-built samples with porosities of ~52–67% exhibited a radial decreasing porosity from the inner layer to the outer layer, and their pore sizes ranged from ~420 to ~630 μm. The compression tests showed the Young's moduli of all the as-fabricated samples (~3.79–~10.99 GPa) were similar to that of cortical bone. The FGM structures built by honeycomb-like unit cells with supporting structure in outer layer exhibited highest yield strength, toughness and stable mechanical properties which is more appropriate to build orthopedic scaffolds for load-bearing application. [Display omitted] •A novel method to design radial gradient porous architecture replicating the gradient structure of bone is proposed.•All FGM scaffolds possess suitable porosity, pore size and elastic modulus for osseointegration.•Scaffold HS exhibited highest yield strength and considerable stiffness, which is suitable for load-bearing application.•Support structures can improve the mechanical properties of the FGMs while maintaining a suitable elastic modulus.•Honeycomb-like unit cells scaffold exhibited better toughness than those with diamond-like unit cells in same porosity.