| The ?-type Ti-24Nb-4Zr alloy has excellent comprehensive properties such as high specific strength,low elastic modulus,good wear and corrosion resistance,no toxic elements,and good biocompatibility,and has become an ideal material to replace traditional biomedical titanium alloys.One.However,titanium and titanium alloys are a biologically inert material with no biological activity on the surface.It is difficult to form a strong chemical osseous bond with the body tissue after implantation in the human body.Long-term use will cause loosening and easily lead to implantation failure.Hydroxyapatite(HA)is the main component of inorganic substances in human bone,and has good biological activity and bone conductivity.However,hydroxyapatite is a brittle ceramic material with poor mechanical properties and is difficult to use as a bone-bearing implant.Therefore,in order to give Ti-Nb-Zr-based ?-type titanium alloy a certain biological activity,domestic and foreign scholars have begun to prepare a series of titanium-based biocomposites based on titanium alloys and hydroxyapatite ceramics as the active reinforcing phase.It also has excellent mechanical properties and high biological activity.In this paper,HA/Ti-24Nb-4Zr biocomposites were prepared by spark plasma sintering technology,and the sintered composites were annealed to improve their plastic toughness.The different HA contents(0%,1%,3%,5%,7%,9%)and different annealing temperatures(750 ?,800 ?,850 ?)on the microstructure,mechanical properties,corrosion resistance and in vitro biological activity and mechanism of composite materials.The main conclusions drawn are as follows:After SPS sintering,the HA/Ti-24Nb-4Zr composite material is mainly composed of ?-Ti phase,?-Ti phase and HA;with the increase of HA content,the needle-like ?-Ti phase in the material increases while ?-Ti phase Decrease;after the HA content is higher than 5wt.%,a small amount of ceramic phase(Ca Ti O3,Ti5P3,Ti2O)formed by the reaction of HA and alloy elements appears in the composite material,and a large number of defects appear on the surface of the material.HA/Ti-24Nb-4Zr composite materials have higher density(97%~99%).With the increase of HA content,the compressive strength and yield strength of the composite material decreased significantly,and the elastic modulus increased slightly.Due to the increase of HA content,the ?-Ti phase increased and the ?-Ti phase decreased and the composite density decreased.Too high HA content will greatly reduce the mechanical properties of the composite material.Due to the effect of the HA brittle ceramic phase,the increase in HA content will also lead to a significant reduction in the plastic toughness of the composite material.At 5wt.%,the compressive strength of 5HA/Ti-24Nb-4Zr composite material is1595 MPa,the yield strength is 1512 MPa,the elastic modulus is 46 GPa,and it has good mechanical properties.After 5HA/Ti-24Nb-4Zr composites were annealed at different temperatures,the microstructure uniformity and mechanical properties were significantly improved.After annealing,the grain size of ? phase becomes smaller,and primary ? phase and secondary ?phase appear in the structure.Annealing treatment has no effect on HA phase;with the increase of annealing temperature,? phase crystals in the composite The grain size increased significantly,the needle-shaped secondary ? phase decreased,and the primary ? phase at the grain boundary decreased;compared with the sintered state,the compressive strength and elastic modulus of the composite after annealing showed a trend of first increasing and then decreasing,and Plastic toughness showed a tendency to decrease first and then increase;after annealing at 850?,the compressive strength,elastic modulus and yield ratio of the composites were 1507 MPa,42GPa and 0.84,respectively,and the overall mechanical properties were improved.With the increase of HA content,due to the increase of ?-Ti phase and pores in the composite material,the corrosion potential of the composite material in the simulated artificial body fluid decreases,the corrosion current density increases,and the corrosion resistance of the composite material increases with the HA content And lower.When the HA content is less than 5wt.%,the composite material has a wider passivation area at the anode and has good corrosion resistance.Compared with the sintered state,the 5HA/Ti-24Nb-4Zr composite material after annealing treatment has higher open circuit potential and higher corrosion potential,lower corrosion current density,and slightly improved corrosion performance,indicating that annealing treatment can improve the corrosion performance of the composite material.After the composite was immersed in simulated artificial body fluid at 37? for 7 days,only a small amount of granular precipitates appeared on the surface of Ti-24Nb-4Zr alloy.With the increase of HA content,more and more bone-like apatite layers on the surface of the composite material,The bone-like apatite layer is clustered on the surface of the material,and is concentrated at the grain boundaries and holes.The 5HA/Ti-24Nb-4Zr composite material after annealing treatment has no significant change in HA content.The morphology and content of the surface bone-like apatite layer after simulated artificial body fluid immersion at37°C have no significant changes compared with the sintered state.The in vitro mineralization performance of the composite material has no obvious effect.In summary,after adding HA to Ti-24Nb-4Zr alloy,the microstructure uniformity,mechanical properties,plastic toughness and corrosion properties of the composite material have decreased to a certain extent,and the in vitro mineralization performance of the composite material has been greatly improved;The best performance is at 5%.Through annealing treatment,the plastic toughness and corrosion performance of 5HA/Ti-24Nb-4Zr composite material are improved;after annealing at 850?,5HA/Ti-24Nb-4Zr composite material has excellent mechanical properties,corrosion properties and in vitro mineralization properties,Can meet the requirements of biological implant materials. |
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