Functionally Graded Metallic Structure for Bone Replacement

Abstract

Processes for the creation and characterization of functionally graded metallic structures for use as artificial bone tissue were investigated. The metallic structure consists of a solid surface layer, a graded porosity layer and a homogeneous porous core. Porous compacts with varied densities were created using traditional powder metallurgy techniques. The surfaces of the compacts were subjected to a densification process with the use of a specially designed indentation tool. Investigations on the effect of the initial density of the compact and the depth of indentation during the deification process on the densified layer and graded porosity region were studied. Compacts with an initial density of 86 % of the true density were indented to depths of approximately 1.8, 1.25, 1, and 0.65 mm. Compacts with initial densities of 67, 70, and 73% were indented to a depth of 1 mm. Optical microscopy and scanning electron microscopy (SEM) were implemented to characterize the morphology of the porous structure. Results show that deeper indentation during the densification process yielded a larger densified layer. The variation of Young’s modulus along the porosity gradation is investigated using micro-indentation. The graded structures are also investigated for fracture parameters and crack growth behavior using digital image correlation techniques.