| Medical Ti-13Nb-13Zr alloy has not only high strength,low modulus of elasticity,good wear resistance and corrosion resistance,but also has the advantages of non-toxic elements and good biocompatibility,which has been widely used in the field of clinical medicine.However,due to the existence of natural inertia,the alloy is difficult to form a stable osseous bond with human bone tissue after implantation,and it lacks the ability of bone integration and active repair of bone defect tissue,resulting in poor biological activity.The porous Ti-13Nb-13Zr alloy can significantly reduce the elastic modulus of the alloy and reduce the"stress-shielding"phenomenon,and it is also conducive to the adhesion,proliferation and crawling behavior of biological tissue on the pore structure,and improve the biological activity of the alloy.However,there is also the problem of a sharp decline in strength,which limits its application.Based on the above problems,this paper,based on the design idea of functional gradient materials,by“gradient functionalized”Ti-13Nb-13Zr alloy,the middle dense Ti-13Nb-13Zr alloy with the porous surface of Ti-13Nb-13Zr/HA composites were designed.By maintaining the good mechanical properties of the middle dense Ti-13Nb-13Zr alloy,the porous surface layer with high porosity can reduce the elastic modulus of the material,and at the same time,the addition of HA ceramic can enhance the biological activity of the material.Therefore,the Ti-13Nb-13Zr-based surface porous composites were prepared by Spark Plasma Sintering(SPS)technology.The effects of sintering temperature and HA ceramic contents on the microstructure,interface bonding,pore characteristics,mechanical properties,electrochemical corrosion properties and in vitro mineralization properties of the composites were investigated.The following conclusions were obtainedThe middle dense Ti-13Nb-13Zr alloy with porous surface of Ti-13Nb-13Zr alloy was prepared by SPS.The alloy matrix was mainly composed of?-Ti and?-Ti phase composition.With the increase of sintering temperature,middle dense matrix relative density increased from89.0%to 95.5%;the grains began to be refined;the microstructure was continuously and uniformly distributed;the interface between the middle matrix and the surface porous layer was stable;the porosity and average pore size of the surface porous layer were decreased,while the compressive strength and elastic modulus of the alloy were increased.The optimized sintering temperature was 1150?.At this temperature,the microstructure of the alloy was uniform;the interface became"fuzzy"and the metallurgical bonding without transition layer was formed;the alloy had good mechanical compatibility(compressive strength value:893 MPa,elastic modulus value:16.0 GPa).At the optimized temperature of 1150?,the surface porous layer of Ti-13Nb-13Zr-based surface porous composites were mainly composed of?-Ti phase,?-Ti phase,HA phase and a small amount of reaction products(Ca3(PO4)2,Ca Zr O3,Ca O,TixPy,Ti2O).As the HA content increased,it inhibited the transition from?-Ti to?-Ti,and the metal-ceramic phase also increased;the surface porosity increased from 34.7%to 55.2%;the average pore size increased from 340.9?m to 503.2?m,and the compressive strength decreased from 893 MPa to650 MPa.In the range of 0-5 wt.%HA,the compressive strength did not change significantly,ranging from 821 MPa to 893 MPa.However,when HA content was higher than 5 wt.%,the sintering quality deteriorated;the interface cracks appeared;the pore connectivity was serious and the pore wall became weak;the integrity of the“gradient”structure was damaged,and the mechanical properties declined sharply.The corrosion resistance of Ti-13Nb-13Zr-based surface porous composites in simulated artificial body fluid(SBF solution)decreased gradually with the increase of HA content,and proper HA content(0-5 wt.%)did not significantly reduce the corrosion resistance of the composites.The ability of composites to induce osteoid apatite formation was gradually enhanced with the increase of HA content.Through the middle dense Ti-13Nb-13Zr alloy and porous surface Ti-13Nb-13Zr/HA composites“gradient structure”designed in this paper.When the sintering temperature was1150?and the HA content was 5 wt.%,it could not only obtain high mechanical compatibility:compressive strength 821 MPa,elastic modulus 15.1 GPa;the pore parameters suitable for the growth of bone tissue cells with average porosity of 47.5%and an average pore size of 400.1?m,it also had excellent bone-like apatite formation ability.It met the conditions of material implantation in human body and has certain clinical application worth. |
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