Study On Passivation Behavior And Passivation Film Characteristics Of Selective Laser Melting Ti-6Al-4V Alloy

Additive manufacturing is a technology that uses CAD data as a blueprint to melt and stack bondable materials such as metal powders,plastics,and ceramics using lasers,electron beams,or plasma arcs to manufacture custom-shaped products or parts.Selective laser melting(SLM)is one of the rapid prototyping technologies.The rapid melting and solidification of metal powders of this technology will definitely have a significant difference in corrosion resistance.This article will discuss the corrosion resistance of this type of material in view of the difference in the structure of this type of material during the laser melting process.Titanium alloys have the advantages of high specific strength,excellent biocompatibility,excellent mechanical properties,etc.,and is widely used in many fields.The selective laser melting technology to prepare metal devices breaks through the limitations of complex structural parts.Compared with traditional methods,it takes shorter time,higher precision,and less material loss,and greatly improves the utilization rate of materials and production efficiency.Although the titanium alloy prepared by selective laser melting has excellent mechanical properties and mechanical properties,whether it has the same excellent corrosion resistance as the titanium alloy prepared by traditional methods has attracted wide attention from domestic and foreign researchers.In this thesis,through the analysis of the microstructure and morphology of selective laser melting(SLM)titanium alloys and annealed titanium alloys,and combined with different application environment,the scientific research system of corrosion resistance and corrosion mechanism of titanium alloy was established.Electrochemical measurement and surface analysis were used to investigate the influence of material structure on the electrochemical process and corrosion products of material corrosion.Scanning electron microscope(SEM),X-ray diffraction(XRD),atomic force microscope(AFM),X-ray photoelectron spectroscopy(XPS)is introduced,and other analytical methods to study the relationship between material organization and corrosion process.It also provides a theoretical basis for the development and application of selective laser melting technology.The main research work of the thesis is as follows:(1)The microstructure of Ti-6Al-4V alloy prepared by annealing and Ti-6Al-4V alloy prepared by SLM was observed by XRD and SEM.By studying the electrochemical corrosion behavior of SLM and annealed samples in human simulated solution at 37 ?,the corrosion resistance was judged,and the relationship between corrosion resistance and structure was studied.The corrosion resistance of metal is closely related to the passive film formed by metal.The passive film structure of Ti-6Al-4V alloy prepared by SLM and annealed alloy in test solution was studied by Mott Schottky.The data of passive film thickness,vacancy density,diffusion coefficient and diffusion flux were obtained by corresponding calculation to further judge the corrosion resistance of metal.(2)The electrochemical behavior and oxide film properties of Ti-6Al-4V prepared by selective laser melting and annealing were investigated in 0.9 wt%,3.5 wt% and 10 wt%Na Cl solution.The effect of chloride concentration on corrosion resistance of metal was studied.The results of Mott Schottky show that the passive film formed on the surface of the two samples in different concentrations of Na Cl solution,and the performance of the passive film is further calculated.