Study On Microstructure And Properties Of TC4 And TC4-5Cu Prepared By Selective Laser Melting

Medical TC4 is the main titanium alloy used in medicine because of its excellent corrosion resistance and biocompatibility.However,as a biologically inert material,TC4 has a weakened bactericidal ability after implantation,and bacterial infection can lead to loosening of the implant or even implantation failure.To solve this problem,consider adding bioactive ion trace element Cu.Using SLM technology,TC4 alloy and TC4-5Cu alloy with antibacterial properties,wear resistance and corrosion resistance can be prepared,and heat treatment can be carried out in the appropriate temperature range,which can minimize the process defects related to porosity,and the microstructure will change,thereby affecting the mechanical properties of the material.In this study,according to the application requirements of medical materials,the biomedical TC4 and TC4-5Cu alloys were prepared by SLM technology,the influence of SLM process parameters on the microstructure,microscopic defects,mechanical properties,wear resistance and corrosion resistance of TC4 and TC4-5Cu alloys was studied,the influence mechanism of Cu elements on the microstructure and properties of formed parts was explored,and the forming process was optimized.Different heat treatment processes were used to heat treat the formed parts,and the influence of heat treatment on the microstructure and properties of the formed parts was studied.The main research contents are as follows:SLM formed TC4 alloy,due to the appearance of fine needle-like martensiticα′structure,the formed alloy shows high hardness,high strength and relatively low ductility,and has good friction and wear properties.The optimized TC4 process parameters:P is 120 W,v is 900 mm/s.The density reached 99.2%,which was 0.6%higher than other parameters;The microstructure grains are fine,and the pores and defects are minimal;Hardness 404.4 HV,yield strength and tensile strength reach 1062.6 MPa and 1223.6 MPa,about 174 MPa higher;The elongation after breaking reached 4.03%,mainly ductile fracture.Compared with atmospheric friction,TC4alloy has a wear rate of 1.88×10^-5mm³·N^-1·m^-1 in 0.9%Na Cl solution,reduced by 16.9%,reduced adhesion surface,narrow wear marks.The wear mechanism is mainly abrasive wear and adhesive wear.SLM formed TC4-5Cu alloy is mainly composed ofα-Ti and Ti₂Cu.The emergence of hard phase Ti₂Cu phase increases the hardness of TC4-5Cu alloy,reduces the elongation after breaking,and effectively reduces the cutting of abrasive particles.The optimized TC4-5Cu alloy process parameters:P is 100 W,v is 800 mm/s.Under this process parameter,there are fewer pores and defects in the microstructure.The average microhardness is 636.7 HV,which is about 35%higher than that of TC4 alloy,the alloy density is 99.03%better,the tensile strength is 936 MPa,the fracture of TC4-5Cu alloy is brittle fracture,and the wear rate of TC4-5Cu alloy in 0.9%Na Cl solution is 1.76×10^-5mm³·N^-1·m^-1。The wear mechanism is adhesion wear and abrasive wear.After heat treatment,TC4 alloyαphase roughened,and theβphase content increased.Compared with other heat treatment processes,the laser remelting performance was better when the remelted layer P was 150 W and v was 900 mm/s,the microhardness was higher by 431.6HV,the tensile strength was 1182.3 MPa,and the elongation after breaking was 5.6%.Compared with the atmospheric environment,the wear rate of TC4 alloy after laser remelting in 0.9%Na Cl solution environment is 1.72×10^-5mm³·N^-1·m^-1,a decrease of 8.99%compared to the atmosphere.The corrosion performance was good,the I_corr was 1.24×10^-7 A/cm²,and the Rp was 2.11×10⁷Ω·cm².Due to the roughening of theαphase and the reduction of the content of TC4-5Cu alloy,the overall strength of the alloy after heat treatment is reduced.When the remelting layer P is120 W and v is 800 mm/s,the laser remelting performance is better,the average microhardness is 548.9 HV,the tensile strength is 704.4 MPa,which is 62.4%higher than other heat treatments,and the elongation after breaking is 1.07%.The wear resistance in 0.9%Na Cl solution is good,and the wear rate is 1.7×10^-5mm³·N^-1·m^-1.The corrosion performance is relatively good,the lowest I_corr is 9.11×10^-8 A/cm²,and the highest Rp is 4.59×10⁶Ω·cm².