| Ti-HA functionally graded material (FGM) is developed as potential material for medical implants. Ti-HA layers with low volume fraction of HA are usually used as internal parts of FGM to withstand heavy load. This paper is focused on the microstructure and mechanical performance of Ti-HA FGM and layers with≤20vol% HA.Ti-xvol%HA (x≤20) composites and FGM (x≤10) were prepared by sintered at 1100℃for 2.5h in Ar atmosphere after cold-pressed at 320MPa. Optical microscope, XRD, SEM and stereological methodology were adopted to analyze the morphological characteristics of ceramic phase and titanium matrix. 3-point bending test was applied to evaluate the mechanical performance of samples.Results showed that Ti and HA reacted to produce CaO and TixPy at high temperature. Ceramic phase was distributed homogeneously in the cavities of titanium matrix as particles of second phase. With the addition of HA, the increase of volume fraction from 8% to 75% and mean particle volume from 102μm3 to 104μm3 was divided into three phases including stable initiation, stimulating term and re-stabilization. Microstructure of titanium matrix was refined by the addition of HA, while diffusion of oxygen to titanium enhanced the deformation along c-axis of titanium crystal lattice.For the sensitivity to addition of HA, linear reduction, density and relative density of samples decreased with the increase of volume fraction of HA. For the porous effect of HA, brittle fracture initiated from the cavities where ceramic phase located, which led to sharp decrease of bending strength from 657MPa to 44MPa and elastic modulus from 75GPa to 18GPa.In FGM, crack occurred sequentially in layers for the relatively weak adhesion of interfaces which were enriched with ceramic phase. Residual thermal stress was relaxed as 17.3MPa (tensile), 2.3 MPa (compressive) and 6.3 MPa (compressive) respectively in layers of Ti, Ti-5vol%HA and Ti-10vol%HA.
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