Performance Control And Biomedical Applications Of Ti6Al4V Manufactured By Selective Laser Melting

Due to superior performances like high strength,low density and corrosion resistance,Ti6Al4 V is extensively applied in various fields such as aerospace and biomedicine,etc.With the increasing demand for lightweight and uni-body spare parts,the levels of integration and complexity increase as well.Limited by the principle of processing,traditional techniques can not live up to the standards of processing complex spare parts.Based on the principle of dotline-plane-body formation,Selective laser melting(SLM)is particularly suitable for manufacturing spare parts with complex structures.As the most widely used titanium alloy material,Ti6Al4 V becomes a focus of the research on the materials for selective laser melting.However,due to the impact of temperature gradient during the forming process,thus reducing the plasticity of Ti6Al4 V samples for SLM forming.Besides,micro defects frequently occur in SLM forming process,which restricts the application of SLMed Ti6Al4 V part.In this paper,property modulation of SLMed Ti6Al4 V part is conducted in three aspects: SLM forming device,SLM process of Ti6Al4 V and heat treatment.The purpose is to improve the overall performance of SLMed Ti6Al4 V.Lastly,the paper studies the medical application of SLMed Ti6Al4 V based on property modulation.The study mainly covers the following aspects:1)SLM forming devices and software function optimization.Firstly,according to existing SLM devices,air circulating vent structures are optimized.Two types of structures are designed to apparently improve the uniformity of recirculating air.Next,the stability of printing process is improved by online monitoring of the forming process.Lastly,nine constraint conditions of fill parameters are put forward by scanning path,so as to enhance the performance of SLM forming Ti6Al4 V.2)Based on the technique control of SLM forming Ti6Al4 V,the paper analyzes the densification of SLM forming Ti6Al4 V,so as to obtain the sample density above 99.5%.βcolumnar crystal is detected on the side of samples with consistent forming orientation,which contains acicular martensite.Because of its impact,the samples indicate high intensity and low plasticity.With the highest technological parameters of density,the tensile strength reaches1210 MPa and the ductility reaches 8.1%,thus meeting the requirement of casting engineering.3)The impact of non-uniformity of recirculating air field on the quality of forming.By analyzing the recirculating air velocity on the sample density and mechanical property,samples are affected by particle deposition,thus reducing density and mechanical property caused by pores.As for low wind velocity,samples are more likely to be affected by splashing particles and smoke dust,which leads to inadequate energy density and generates pores.The Pearson correlation coefficients of circulating airflow velocity and the rate of sample elongation at break demonstrate an apparent and positive correlation between the two factors.4)The organization regulation of SLM samples is conducted through the annealing heat treatment.After the annealing heat treatment,the microstructures convert from α′ acicular martensite to the mixture of α phase and β phase.Microhardness and tensile strength decline as the heat treatment temperature increases,while the ductility at break gradually rises.At the heat treatment temperature of 950℃,the maximum ductility at break of 14.1% is obtained,which is74% higher than the forming samples.Besides,the tensile strength is still above 1000 MPa,and the mechanical property lives up to the standard of Ti6Al4 V forge piece utilization.5)Applied research on spinal implants and pelvis plates is carried out.Based on model design-simulation analysis-SLM forming,spinal implants of SLM forming Ti6Al4 V are verified.As for pelvis plates of SLM forming Ti6Al4 V,the key points are concluded based on design,data process and SLM forming,thus providing some references to subsequent applications.