Optimal design and fabrication of hydroxyapatite–Ti asymmetrical functionally graded biomaterial

Abstract

Hydroxyapatite (HA)–Ti asymmetrical functionally graded biomaterial (FGM) combining the excellent biocompatible properties of HA ceramic and the good mechanical properties of titanium metal was designed optimally and fabricated in this paper. The thermo-elastic properties of the uniform HA–Ti composites with various mixing ratios corresponding to each graded layer of the FGM were tested firstly. The experimental results show thermal expansion coefficients of HA–Ti composites increase with the rise of testing temperature or the content of HA ceramic and aren't affected by the allotropic transformation of α→ β-Ti phase at 882.5 °C, while there is no a direct corresponding relationship between elastic modulus and the mixing ratio of HA–Ti composites. Then the optimal graded compositional distribution exponent n for HA–Ti asymmetrical FGM is acquired by the thermal stress relaxation design and structure optimization, which is 0.9. Finally the perfect HA–Ti asymmetrical FGM with the optimum graded composition was fabricated by hot pressing successfully. The tested values of residual thermal stress in the sintered FGM samples by X-ray stress analyzer are basically consistent with the theoretically calculated ones.