Preparation, Microstructure And Properties Of Degradable β-TCP/Zn-Mg Composites

Because zinc（Zn）and its alloys have suitable corrosion degradation rate and Zn is one of the essential trace elements in human body.The application of biodegradable zinc alloys in bone screw and cardiovascular scaffold has attracted extensive attention in recent years.However,the mechanical properties of pure Zn are too poor to meet the clinical requirements.In order to improve the mechanical properties and biocompatibility of pure Zn,alloying combined with appropriate deformation process is an effective way to improve mechanical properties and biocompatibility.In addition,the preparation of Zn matrix composites by adding ceramic particles with good biocompatibility can not only improve the mechanical properties,but also improve the biological activity.In this paper,Zn-1wt.%Mg alloy as matrix andβ-TCPceramicparticlesasreinforcementwereusedtoprepare Zn-1wt.%Mg-nvol.%β-TCP（n=0,1,3,5）composites by melting and powder metallurgy methods,the microstructures,mechanical properties,corrosion degradation behavior and biocompatibility of the composites were studied;and the effects of the content ofβ-TCP ceramic particles on the properties of Zn-1wt.%Mg-nvol.%β-TCP（n=0,1,3,5）composites were discussed.The conclusions of this study were as follows:（1）The phase of Zn-1wt.%Mg-nvol.%β-TCP（n=0,1,3,5）composites prepared by melting method is mainly composed of Zn matrix and the second phase is mainly Mg₂Zn₁₁ phase distributed along grain boundary.Because of theβ-TCP can refine grain size,with the increase of the content ofβ-TCP,the grain size of composites decreases gradually.However,the agglomeration ofβ-TCP is more obvious.After hot extrusion,the grain size is refined and the agglomeration ofβ-TCP ceramic particles is alleviated.With the increase of the content ofβ-TCP,the mechanical properties were improved first and then decreased.The results show that the Zn-1Mg-1vol.%β-TCP composite has good comprehensive mechanical properties.The maximum tensile strength is 330.5 MPa,yield strength is 250.8 MPa and elongation is11.7%.（2）The Zn-1wt.%Mg-nvol.%β-TCP（n=0,1,3,5）composites’change trend of corrosion degradation rate is consistency measured by electrochemical and in vitro immersion weightlessness methods.The results show that,increasing the content ofβ-TCP can reduce the corrosion resistance and accelerate the corrosion degradation rate of the composites and the results show that the prepared materials have a suitable corrosion degradation rate.（3）Theβ-TCP in Zn-1Mg-nvol.%β-TCP（n=1,3）prepared by powder metallurgical method can be uniformly dispersed in Zn-Mg matrix but the interface bonding is very poor.Compared with the composite prepared by melting,the composites prepared by powder metallurgy has low density.As a result,it’s mechanical properties are also poor.The maximum compressive strength and compressive yield strength of Zn-1Mg-3vol.%β-TCP composites are 108.9 MPa and 99.1 MPa,respectively.（4）The corrosion degradation behavior of Zn-1wt.%Mg-nvol.%β-TCP（n=1,3）composites prepared by powder metallurgy was characterized by electrochemical method and in vitro immersion weightlessness method.The results show that with the increase ofβ-TCP content,the corrosion resistance decreases,and the low density of composites can accelerate the corrosion to a certain extent.（5）The experiment in vitro cytotoxicity and implantation in SD rats improved that compared with Zn-1Mg alloy,the Zn-1Mg-nvol.%β-TCP（n=1,3）composites have better biosafety,biocompatibility and biological activity.