Laser Additive Manufacturing Of Medical β Titanium Alloy And Performance Resarch

β titanium alloy has high strength,wear resistance,excellent biocompatibility,low elastic modulus,and is widely used in the field of medical surgery.However,the elastic modulus of medical β-titanium alloys is often higher than that of human bones,which makes it difficult for them to better fuse with the biological body.This article aims to prepare low titanium alloy elastic modulus and explore the trend of changes in the coating structure and properties with Mo and Nb element content.The specific research content is as follows.Firstly,the stability and elastic properties of binary Ti-Mo alloys and ternary Ti-Mo-Nb alloys were calculated using first-principles calculations.The stability calculation results show that as the Mo and Nb content increases,the system’s free energy and binding energy both decrease,and the difference between the elastic constants C11-C12 is greater than 0 and shows an increasing trend.The energy of the system in the DOS at the Fermi level decreases,indicating that the stability of the system gradually improves.The elastic property calculation results show that in the Ti-Mo system,as the Mo content increases,the Young’s modulus shows a trend of decreasing first,then increasing,and then decreasing again.When the Mo content is 20%,the Young’s modulus reaches its lowest value of 64.34 GPa.The bulk modulus reaches its highest value of 148.72 GPa when the Mo content is 20%,demonstrating good resistance to deformation,while the shear modulus reaches its highest value of 27.25 GPa when the Mo content is 10%,demonstrating good resistance to shear.In the Ti-Mo-Nb system,the Young’s modulus shows a trend of initially decreasing and then increasing with the increase of Nb content,which is lower than that of the Ti-Mo binary alloy overall.The bulk modulus and shear modulus both reach their highest values of 131.16 GPa and 23.94 GPa,respectively,when the Nb content is 5%.In addition,through crystal anisotropy simulation,it was found that both systems grow first along the <1,1,1> crystal direction and then along the <1,0,0>crystal direction.Moreover,with the increase of Mo and Nb content,the anisotropic characteristics become more prominent.Secondly,Ti-Mo binary alloy and Ti-Mo-Nb ternary alloy coatings were prepared using laser cladding technology.XRD experimental results show that the peak value of the main diffraction peak of the Ti-Mo binary alloy gradually increases with the increase of Mo content,from a β+α phase to a single β phase,as well as a secondary diffraction peak α phase.The Ti-Mo-Nb ternary alloy also consists of α and β phases,but unlike the Ti-Mo binary alloy,the main diffraction peak of the Ti-Mo-Nb ternary alloy is completely presented by a single β phase.Microstructure test results show that with the increase of Mo content in the Ti-Mo binary alloy,the equiaxed grain size gradually decreases,while for the ternary Ti-Mo-Nb system,the equiaxed grain size gradually increases with the increase of Nb element content.In addition,with the increase of Mo content,the morphology of martensitic structure in the Ti-Mo binary alloy coating gradually changes from plate-like to needle-like.While in the ternary Ti-Mo-Nb alloy coating,with the increase of Nb element content,the martensitic structure becomes fine and needle-like.Thirdly,the influence of Mo and Nb content on the mechanical properties of the coatings was analyzed,and the friction and wear mechanism of the coatings was investigated.Hardness test results show that as the Mo content increases,the hardness of the Ti-Mo binary alloy coating shows a trend of increasing first and then decreasing,with an average hardness of about 450 HV,higher than that of the Ti-Mo-Nb ternary alloy.Tensile test results show that the Young’s modulus of the Ti-Mo binary alloy coating shows a trend of first decreasing and then increasing,with an average value of about 30 GPa.When the Mo content is 25%,the Young’s modulus reaches its lowest value of29.47 GPa,while the coating exhibits high tensile strength of 393.79 MPa and yield strength of 206.67 MPa.The Young’s modulus of the Ti-Mo-Nb ternary system coating is lower than that of the Ti-Mo binary alloy coating and shows a trend of first decreasing and then increasing.When the Nb element content is 5%,the Young’s modulus reaches its highest value of 13.19 GPa,while when the Nb content is 10%,the Young’s modulus reaches its lowest value of 7.95 GPa.Friction and wear test results show that the optimal friction performance of the Ti-Mo binary alloy and Ti-Mo-Nb ternary alloy occurs at Mo content of25% and Nb content of 5%,respectively,with values of 0.369 and 0.492.Finally,the corrosion resistance of the coatings and their mechanism were studied in physiological saline solution containing 3% NaCl.The results of electrochemical corrosion tests show that when the Mo content is 25%,the TiMo binary alloy has a high corrosion potential and a large impedance curvature under open circuit potential,but also a fast corrosion rate.In the Ti-Mo-Nb system,when the Nb content is 20%,the corrosion voltage is highest at about-0.22 V under open circuit conditions,and under electric conditions,the alloy still remains at a relatively high corrosion potential,but the corrosion rate is still relatively fast.The corrosion surface morphology showed that the number of pitting holes significantly decreased when Nb was added to the Ti-Mo binary alloy.