Radially graded porous structure design for laser powder bed fusion additive manufacturing of Ti-6Al-4V alloy

Abstract

Porous structures have been used in many areas particularly in medical, transportation, space and defense applications. The building of porous structure is formed by the lattices which have many unusual and interesting features that make them candidates for innovative designs. Such designs include creating porosity variation in structures and the aim is to achieve exceptional mechanical and biological efficiencies in terms of strength, stiffness, energy absorption capacity, and stimulating tissue ingrowth. In this paper, a design approach for uniform and graded porous structures is proposed to be produced by additive manufacturing. Pores were radially graded inside to outside by changing the lattice strut thickness, and vice versa. The additively manufactured structures were characterized by laboratory tests in the scope of producibility, morphological, chemical, and mechanical performance via caliper, precision scales, uniaxial compression test, optical light, and scanning electron microscope. The findings confirm that the wide range of porosities (60– up to 80 %) were achieved by using different strut thickness. Besides, porous structures with a wide range of density ratio from 0.88 to 1.22 g/cm3 were revealed by applying porosity variation strategies. The graded porous structures were evaluated based on their specific compressive strengths. The results have also shown that the density of struts, which increased radially inward to outward facilitated a 6% improvement. Deformation mechanism and failure behavior of the structures were strongly affected by the porosity variation strategy. The graded porous structures were found to exhibit distinct deformation behavior when compared to a uniform porous structure, where the energy absorption capacity is higher in graded porous structures compared to uniform structures.