Research On Interfacial Microstructure And Properties Of Implantable Al₂O₃/Ti-13Nb-13Zr Diffusion Bonding Joints

The bonding structure of Al₂O₃ ceramics and titanium alloy has wide application prospects in the field of implantable medical devices.Al₂O₃ ceramic has good wear resistance,corrosion resistance,biocompatibility and chemical stability,and is a bio-ceramic material with excellent performance.At current stage,the titanium alloys used in implantable devices in China are mainly pure titanium and TC4,while the service period of pure titanium is short after implantation,and the vanadium element in TC4 has biological toxicity.Therefore,this subject selects Al₂O₃ ceramics and new medical titanium alloy Ti-13Nb-13Zr that do not contain toxic elements for diffusion bonding research;explores the optimal process parameters of the joints;analyzes the effects of different parameters on the interface structure and mechanical properties of the joints;established the relationship between the interface structure and mechanical properties,and studied the electrochemical corrosion behavior of the optimal joint and the base material in different simulated body fluid environments,aiming to achieve effective bonding of long-term implantable ceramic/titanium alloy structural parts.In this subject,the effective bonding between Al₂O₃ ceramic and Ti-13Nb-13Zr alloy is achieved by diffusion bonding.The interface structure of typical joint is Al₂O₃ceramic/Ti O₂/Ti Al+Nb₂O₅+Al Nb₂/Ti₃Al layer+needle Ti₃Al+β-Ti（s,s）/Ti-13Nb-13Zr alloy.In this bonding system,the Nb element plays a key role.The Ti O₂,Nb₂O₅ and Al Nb₂ particles generated in the Ti Al reaction layer play a role in dispersion strengthening against the joint,and inhibit the growth of the Ti-Al brittle layer and improve mechanical properties of the joint.The increase of bonding temperature or the extension of holding time will promote the element diffusion and interfacial reaction between the base materials,so that the thickness of the Ti₃Al layer and Ti Al layer in the interface increases,and the amount of Nb₂O₅ and Al Nb₂ in the Ti Al layer increases first and then decreases.In addition,this subject reveals the evolution of the joint structure with temperature,and analyzes the growth kinetics of the interface reaction layer at the joint.The influence law of process parameters on mechanical properties of joints was clarified by room temperature shear test.The factors of bonding temperature,holding time and bonding pressure have a significant effect on the joint interface structure,mechanical properties and macroscopic deformation of the structural parts.The shear strength of the joint increases first and then decreases as temperature or holding time increases.When the bonding process parameter is at 1175℃/60min/3MPa,the optimal joint is obtained,and its shear strength is 52.0MPa;when the pressure is 1MPa,the interface bonding is not good;when the pressure is greater than 5MPa,although the shear strength of the joint is improved,the Ti-13Nb-13Zr alloy is severely deformed and loses its application value.Hence the optimal pressure parameter is 3MPa.There are three types of joint fracture paths.The fracture path type of optimal joint is ceramic fracture.The corrosion resistance of the optimal joint and Ti-13Nb-13Zr base material in Ringer’s solution and Hank’s balanced salt solution was analyzed by electrochemical test.By comparing the open circuit potential,polarization curve and impedance spectrum of the optimal joint and Ti-13Nb-13Zr base material in the same and different solutions,the corrosion resistance in different environments was analyzed.