Study Of The Fabrication Process And Properties Of Selective Laser Melting Fabricated LaB₆ Reinforced Titanium Alloy

With the wide range of applications of titanium alloys in the medical field,their defects of low hardness and poor wear resistance have gradually become prominent,which has limited their development in the medical field.In this paper,LaB₆/Ti-6Al-4V composite samples were prepared by selective laser melting technology.In situ chemical reaction of 12Ti+2LaB₆+3[O]=12TiB+La₂O₃ was used as a means.The strength,hardness and wear resistance of titanium alloy is improved by multi-scale enhancement effect of TiB and La₂O₃.In this paper,the influence of LaB₆ reinforcement phase content and forming process parameters on the formability,microstructure and mechanical properties of the sample was studied.Finally,the optimal LaB₆ content and forming process parameters were used to prepare dental implants with excellent performance.The main findings of the study are as follows.Firstly,the effect of LaB₆ content on mechanical properties of composites was studied,and the microstructure evolution mechanism of Ti-6Al-4V samples under different LaB₆ content was explored.The results showed that the relative density of samples decreased with the increase of LaB₆ content.Due to the influence of Marangoni flow in the molten pool,with the increase of LaB₆ content,the sample microstructure changed from discrete needle structure to dendritic structure,and finally developed into cellular structure.After adding LaB₆ to titanium alloys,the hardness,wear resistance,and strength of the composite are enhanced due to grain refinement strengthening,dispersion strengthening,and solid solution strengthening,while the plasticity of the material is lost.The 3 wt.%LaB₆ sample has the most significant strengthening effect.Compared to the 0 wt.%LaB₆ sample,the hardness is increased by 35.71%,the wear volume is reduced by 47.5%,the tensile strength is increased by 14.5%,and the elongation after fracture is reduced by 37.2%.Besides,the 0.5 wt.%LaB₆ sample has the best formability and is most suitable for production practice.Second,the effects of laser power on the forming quality,microstructure evolution,and mechanical properties of composite samples were investigated.The results show that the sample forming quality is related to the laser power.The microstructure of the composite material is granular,needle-like reinforcement,and the elongatedα-Ti phase is uniformly distributed.With the increase of laser power,the length and width of theα-Ti phase and the size of the reinforcement phase in the sample gradually increase.Under the conditions of scanning speed of 500 mm/s,scan spacing of 0.12 mm and coating thickness of 0.03 mm,the comprehensive mechanical properties of the sample are the best when the laser power is 260 W.Compared with the laser power of 225 W,the hardness of the sample increases by 29.64 HV,the wear volume decreases by 37.2%,and the tensile strength increases by 138.1 MPa.The elongation at break of all composites is small,ranging from 5%to 6%.Finally,based on the previous research,the composite powder with LaB₆ content of 0.5 wt.%was selected as the raw material for Selective laser melting preparation of dental implant parts,and the laser power was set to 260 W,the scanning speed was 500mm/s,scan spacing of 0.12 mm and coating thickness of 0.03 mm.Compared with the Ti-6Al-4V samples,the strength and corrosion resistance of the TiB+La₂O₃/Ti-6Al-4V samples prepared at this time is significantly improved.