Hydroxyapatite-Ti functionally graded biomaterial fabricated by powder metallurgy

A functionally-graded biomaterial (FGM) in a hydroxyapatite (HA)-Ti system was developed by an optimized powder metallurgical process and investigated by microstructural analysis and mechanical tests. The constituents in sint ered HA-Ti FGM distribute gradually with the variation in chemical composit ion, eliminating the macroscopic interfaces, such as that in HA-Ti direct j oint. Partial decomposition of HA phase was found in interlayers of the FGM due to the co-existence of Ti during sintering. Mechanical properties in H A-Ti FGM also exhibit gradient distributions. Vickers hardness and Young's modulus are strongly affected by the porosity. However, bending strength an d fracture toughness increase remarkably with the rise of Ti content, espec ially in the Ti-rich region. Maximum strength and toughness (971.96 Mpa and 29.691 MPam(1/2) respectively) were reached in the pure Ti layer, which ar e far higher than those of human bone. In addition, the strengthening and t oughening mechanism was discussed. In summary, HA-TI FGM is a promising bio material for use as a hard-tissue replacement implant, considering its mech anical behaviors. (C) 1999 Elsevier Science S.A. All rights reserved.