Study On Preparation Technology And Optimization Of Microstructure And Properties Of Porous Metal Titanium And Titanium-cobalt Alloys

Porous titanium has excellent biocompatibility,corrosion resistance and high specific strength.Which has a wide application prospect in the field of biological implant materials and engineering applications.In order to systematically study and optimize the preparation technology of porous titanium and its alloy,the effects of cobalt on porous titanium tissue,structure and compressive properties were systematically studied.Porous titanium and porous titanium cobalt alloy were prepared by powder metallurgy technology.The effects of process parameters and Cobalt powder addition on the pore structure,phase composition,microstructure and mechanical properties of the samples were discussed by metallographic examination,XRD phase analysis,SEM test,microhardness test and compression resistance test.The following conclusions are drawn:?1?The pressing pressure can change the density of raw billet,the tightness of the binding of titanium particles and improve the growth of porous sintered neck.The smooth removal of urea and the high densification of raw billets are contradictory,so the higher impacting pressure will lead to the formation of the internal and external defects of the specimen,which is not conducive to the preparation of porous titanium with excellent structure.When pressing pressure is 150 MPa,titanium foam has the best pore structure and mechanical properties.?2?Sintering parameters can significantly influence the structure and properties of porous titanium.The increase of sintering temperature and the prolongation of sintering time can contribute to the diffusion of atoms and the continuous growth of sintered neck,so as to achieve better metallurgical bonding.Porous titanium sintered at 1100?has the characteristics of high connectivity and large pore size;When the sintering time is1.5h,the densification degree of the hole wall is better and the pore size is suitable for the pore structure.?3?The content of pore forming agent is an important factor affecting pore structure.When the urea content is above 50Vol%,porous titanium with high pore connectivity,various pore structures and pore shape is prepared using fine urea particles as pore forming agent in this experiment.This greatly improves the permeability of porous titanium and has excellent characteristics as biological implantation.?4?Under the same preparation parameters,porous titanium cobalt alloy with porosity of 22.72⁴5.20%was prepared by adding cobalt alloy powder with different mass fraction.The microhardness of porous materials is 277.45⁵74.40Hv,and the compressive yield strength is 210.85⁴08.27MPa.The addition of cobalt powder can significantly improve the density of porous titanium pore wall and improve the mechanical properties of porous titanium.From the fracture surface analysis of porous titanium,it can be concluded that the failure of porous titanium during compression is mainly brittle fracture because of obvious"river pattern"and the smooth surface on the fracture surface.The addition of appropriate amount of cobalt powder resulted in some lumpy Ti₂Co discontinuously distributed at the grain boundary of the titanium and Ti and Ti₂Co composed of layered tissue in the pore wall of the porous material,which greatly improves the mechanical properties of the materials.And the fracture morphology is characterized by ductile fracture with shallow dimples.However,when the addition of cobalt is too much,the Ti₂Co around the grain boundary of the titanium on the hole wall is continuously distributed in a network.Although the porosity decreases,the mechanical properties of the materials may be deteriorated by the fracture of the compression failure along the Ti₂Co phase...