| Ti6A14V alloy is widely used in orthopedic and dental areas due to its good comprehensive properties,but it shows bio-inert,and cannot prevent and solve the implant-related clinical infections.Once the infection occurs,it will bring heavy economic burden and great pains to the patients.In recent years,there have been studies showing that the addition of cooper(Cu)to metal materials can endow the materials with antibacterial properties and various biological functions.The Cu-containing antibacterial metal materials show great application prospects as a new type of biomedical material.Therefore,in this thesis,Cu was added to the Ti6A14V alloy for preparing antibacterial Cu-bearing Ti6Al4V-xCu alloys.The optimum hot-processing parameters,heat treatment and Cu content for the Ti6A14V-xCu alloys were studied to obtain the best comprehensive performance of alloys.Three kinds of Ti6Al4V-xCu alloys,with Cu contents of 4.5,6 and 7.5 wt.%,were prepared in this thesis.Then,the optimum heat treatment was obtained by controlling temperatures and cooling rates of heat treatments,and the relevant antibacterial mechanism was studied.In addition,the heat treatment process of Ti6Al4V-xCu(x=4.5,6 and 7.5 wt.%)alloys were further optimized in a smaller temperature range,and the optimum Cu content was studied.Finally,based on the above studies,the alloy with a composition of Ti6Al4V-5.5Cu was prepared,and a series of experiments were conducted to prove whether the performance of the alloy met the requirements of implant material.The main conclusions are as follows:(i)Through Gleeble compression tests,the constitutive equations of Ti6Al4V-xCu(x=4.5,6 and 7.5 wt.%)alloys were obtained as follows:Z=εsexp(421206.8/RT)=1.19×1016[sinh(0.0098σ)]3.12Z=εexp(422834.4/RT)=2.79×10-6[sinh(0.0098σ)]3.02Z=ε8exp(350379.1/RT)=1.95×10-3[sinh(0.0104σ)]2.96According to the hot processing maps of these three alloys,the stable hot-processing areas of Ti6Al4V-4.5Cu and Ti6A14V-6Cu alloys were larger than that of the Ti6A14V-7.5C u,which indicated better thermal deformation property of Ti6Al4V-4.5Cu and Ti6Al4V-6Cu alloys.Combining the hot processing maps and the microstructure observations of different alloys,the optimum deformation parameters for getting good equiaxed microstructures of the Ti6A14V-xCu(x=4.5,6 and 7.5 wt.%)alloys are as follows:Ti6Al4V-4.5Cu alloy:750％/0.001-0.01 s-1 and 800 ℃/0.001 s-1;Ti6Al4V-6Cu alloy:750 ℃/0.001～0.01 s-1 and 800 ℃/0.1 s-1;Ti6Al4V-7.5Cu alloy:750 ℃/0.001 s-1 and 800 ℃/0.1 s-1.Meanwhile,in the single phase region,the optimum deformation parameters for obtaining microstructures with higher degree of recrystallization are as follows:Ti6Al4V-4.5Cu alloy:950 ℃/0.1 s-1,1000/0.1 s-1;Ti6Al4V-6Cu alloy:950 ℃/0.01 s-1,1000 ℃/0.1 s-1;Ti6A14V-7.5Cu alloy:900 ℃/0.01 s-1,950 ℃/0.01 s-1,1000 ℃/0.01 s-1.In conclusion,the strain rates of hot-processing should be slow,and the workability of the Ti6Al4V-xCu alloys is sensitive to the Cu content.The more the Cu content in the alloy,the lower the strain rate for the hot-processing.(ii)For the Ti6Al4V-4.5Cu alloy,the optimized heat treatment that endows the alloy with good mechanical properties,corrosion resistance and antibacterial activity is annealing at 740 ℃ for 1 h and cooling in air.What’s more,the larger size of Ti2Cu particles and massive β phase in the equiaxed microstructure make the alloy show better antibacterial properties than that possessing thin O/Ti2Cu lath microstructure.(iii)The heat treatments of the Ti6Al4V-xCu(x=4.5,6,7.5 wt.%)alloys were further optimized in a narrower temperature range,and the optimized heat treatments for each alloy are annealing at 720 ℃,740 ℃ and 760 ℃ for 1 h,respectively,with cooling in air.Meanwhile,the addition of Cu should not be higher than 6 wt.%to make the alloys possess satisfied comprehensive properties.(iv)Based on the above results,a Cu-containing titanium alloy with composition of T16A14V-5.5Cu was prepared.To evaluate the comprehensive performances of the alloy,a series of experiments were conducted.The results showed that comparing to the Ti6A14V alloy,the fatigue strength,hardness,yield strength,tensile strength,and elongation of Ti6A14V-5.5Cu alloy were increased by 13%,21%,11.6%,11.4%,and 6.3%,respectively.Meanwhile,the uniform corrosion resistance of Ti6Al4V-5.5Cu alloy was also comparative to the Ti6A14V alloy.What’s more,the Ti6A14V-5.5Cu alloy showed excellent antibacterial property and no cytotoxicity.In conclusion,by the optimization of hot-working process,heat treatment and Cu content,Ti6Al4V-Cu alloy shows excellent comprehensive properties,including good tensile properties,wear resistance,fatigue properties,corrosion resistance,antibacterial property and no cytotoxicity.As a new type of biomedical metallic material,Ti6A14V-Cu alloy has broad application prospects. |
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