The Research On Graphene-regulated Functional Titanium With High Strengh And Hign Porosity By 3D Printing

Prous titanium material is a new functional material due to its low density,high strength,wide working temperature range,good corrosion resistance and good biocompatibility.However,the current porous titanium most is porous Ti-Al-V titanium alloy,some of which contain vanadium and aluminum elements are harmful to human body.The most common preparation method for porous titanium arc powder metallurgy and slurry foaming,these methods can not accuraterly control the structure and shape of porous titanium holes.For this reason,we used 3 D printing technology to prepare porous titanium,and accurately control the structure of porous titanium hole and the shape of porous litanium.Then.added graphene to enhanced strength of pure titanium.Firstly,graphene powder and spherical titanium powder were mixed by ball-milling to obtain porous titanium with different pore shape and structure by selective laser mclting(SLM)technology.then the physical and mechanical properties were studied systematically.and the mechanism of reaction between graphene and titanium was analyzed.he key results are as follows:(1)The low-cost 200-mesh hydrogenation-dehdrogenation titanium powder was mixed with the average diameter 75? spherical titanium powder at a mass ratio of 2:8 for selective laser melting.when laser power 100 W.scanning speed 550 mm/s,scanning spacing 60?m,spot diameter 45?m,powder layer thickness 25?m,laser energy density 121 J/mm3,the density of bulk pure tianium materials prepared is 98.7%.The spherical titanium powder with an average particle size of 30?m mixed by ball-milling with 1%graphene nanoplatelets(GNPs)for selective laser melting.When the laser power is 70W,the scanning speed it 600 mm/s,the scanning distance is 60?m,the spot dimeter is 45?m,the layer thickness is 25?m,the laser energy density is the laser energy density is 78 J/mm3,the density of the bull material is 99.38%,and the compressive yield strength is 955MPa.With same laser process,the density of pure titanium bulk materials formed by spherical titanium powder with an average diameter of 30?m was 98.62%and the compressive yield strength was 597MPa.(2)A honeycomb porous titanium model with a preset porosity of 81.2%was printed out by selective laser melting technique.Porous titanium without graphene,the porosity is 57.87%,microvickers hardness is 236HV,elastic modulus is 34.317GPa,compressive strength is 277.58MPa.The porous titanium with 1%graphene with porosity of 58.9%,microvickers hardness of 503HV,elastic modulus of 36.151GPa,compressive strength of 317.38MPa.The corrosion potential of porous titanium with 1%graphene was increased to-0.325 V,and the corrosion rate was reduced to 4.32×10-7A/cm2,the corrosion resistance was better than that of porous titanium without graphene.(3)The porous titanium with 1%graphene was heated to 500? for 0.5 hours.After heat treatmen,compared with SLMed sample,the microvickers hardness is 430HV,reduced 14.5%,the elastic modulus is 34.457 GPa,is 4.7%lower,and the compressive strength is 345 MPa,9.2%increase.The corrosion resistance of porous titanium decreased,corrosion potential decreased to-0.392V,and corrosion rate increased to 3.87×10-7A/cm2.The hardness of the porous titanium decreases but the strength increases after heat treatment,which is due to the recovery and recrystallization during the heat treatment process,while eliminating the residual stress in the porous matrix and avoiding the damage caused by the microcracks caused by the residual stress in the compression process in the supporting rod of the porous body.(4)During laser selective melting,the graphene partly reacted with titanium at the interface of graphene and titanium to form titanium carbide,and the titanium carbide disperses in the matrix of porous titanium.However,after the heat treatment,graphene did not react further with titanium,and the graphene still existed in the porous titanium matrix,due to the low heat treatment temperature and the existing titanium carbide layers around the graphene lamellae during selective laser melting.