| P-type Ti-Nb-Zr-X biomedical alloy is expected as a biomedical implant material widely used in clinical applications because of its low modulus of elasticity,high compressive strength,good corrosion resistance.However,titanium alloy is a bio-inert material,the osseointegration is difficult formed between the surface of the Ti alloy implants and the bone tissues,then,affecting the working life of the implant.Based on this,in this paper,the process of functional composite is developed between the Ti-35Nb-7Zr alloys with excellent mechanical properties and the bioactive ceramic of hydroxyapatite(HA)according to the idea of synergistic control of Ti,Nb and Zr contents in composites.The contents of Ti,Nb and Zr are replaced by hydroxyapatite(HA)at the mass ratio of Ti;Nb:Zr = 58:35:7,to maintaining the mechanical properties of?-type matrix advantage and improving the biological activity of titanium alloy.Ti35Nb7Zr/HA biocomposites were fabricated by spark plasma sintering(SPS).The effects of HA contents(0 wt.%,5 wt.%,10 wt%,15 wt%,20 wt.%)and sintering temperature(900? 1000?,1100?,1200?)on microstructure evolution,relative density,mechanical properties,corrosion properties and in vitro bioactivity of the composites were investigated.The Ti35Nb7Zr/HA biocomposites are mainly consisted of ?-Ti phase,a small amount of?-Ti phase and ceramic phase(Ti2O,CaTiO3,CaZrO3,CaO,TixPy).With the increase of the HA content,the ?-Ti phase decrease,while the a-Ti phase and ceramic phase increase obviously.The ceramic phase is uniformly dispersed in the matrix and pores.With the increase of sintering temperature,the content of ?-Ti phase and ceramic phase increases,and the content of a-Ti phase decreases.The distribution of material in the composites is more uniform.The granular ceramic phase precipitates along the substrate grain boundary or within the grain,which gradually grow,merge,and finally distributed around the titanium matrix and inside the matrix grains.The relative density of the composites decreases with the increase of the HA content,and increases with the increase of the sintering temperature.With the increase of HA content,the compressive strength of the composites decreased from 1736 MPa to 958 MPa,and the elastic modulus increased from 45 GPa to 55 GPa.With the increase of sintering temperature,the compressive strength of the composites increased from 1020MPa to 2279MPa,and the elastic modulus increase5d from 44.8GPa to 61 GPa.The mechanical properties of the composites vary depending on the content,distribution and structure of the ceramic phase.The high elastic modulus of the ceramic phase results in an increase in the modulus of elasticity of the composite.The more uniform the distribution of the ceramic phase in the composite material,the higher compressive strength of the composites.When the sintering temperature is high,the resulting mesh-like ceramic phase increases the compressive strength of the composite.Due to the role of the ceramic hard phase,the composite material exhibits a typical brittle fracture during compression.With the increase of HA content,the corrosion current density of the composites gradually increased,indicating that the higher the HA content,the lower the corrosion resistance of the composites.The corrosion tendency of Ti35Nb7Zr/5HA and Ti35Nb7Zr/10HA composites is similar to that of Ti35Nb7Zr alloy.Ti35Nb7Zr/5HA and Ti35Nb7Zr/10HA have a wide passivation area in the anode region.The corrosion current density of Ti35Nb7Zr/5HA and Ti35Nb7Zr/10HA is almost the same as that of Ti35Nb7Zr alloy,and it shows good corrosion resistance.With the increase of HA content,the bone-like apatite deposition on the surface of Ti35Nb7Zr/HA biocomposites increased with Ti35Nb7Zr/HA composites were immersed in artificial simulated body fluids for 7 days,shows that the ability of composite materials to induce bone-like apatite formation is gradually enhanced.Bone-like apatite deposition is a process for nucleation-the continuous growth.The composites surface of the ceramic hole provided with energy and nucleation positions,leading to the bone-like apatite nucleation and grow up,finally formed a uniform bone apatite layer.Composites exhibited good mineralization ability in vitro,and have excellent in vitro bioactivity. |
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