Research On Process Of Laser Shock Melt Injection Fine RE Particles Into Aluminium Alloy Surface And Modified Layer Properties

Aluminum alloy conductors are the core components of Gas Insulated Substation known as the neural node of Modern Smart Grid;silver plating,however,as a mainstream treatment process to enhance conductivity of electrical connection terminals of aluminum alloy conductors,has the problems that the coating is easy to peel off and coating present pollution problems in the manufacting process.It can be seen that it is of great research significance to seek a process that can modify electrical connection terminals of aluminum alloy conductors instead of silver plating process.Based on the review of relevant research at home and abroad,this article puts forward a new idea"Using laser shock melting technology generate a rare earth modified layer in situ on the surface of aluminum alloy,so as to exploit the advantages of laser surface modification and the multiple mechanisms of action of fine particles.As a result,replacing silver plating to solve the problems of easy peeling of the plating and pollution in the electroplating process".In the study,A356 aluminum alloy was used as the object,and the fine cerium oxide was used as the modified material.Based on the numerical analysis of laser shock injection of Ce O_2pon the surface of the aluminum alloy,the optimal melting process under the experimental conditions are abtained and structure features of different areas of modified layer are analysised.Investigating its performance characteristics of the conductivity,oxidation resistance,corrosion resistance and so on,and preliminarily discuss the mechanism of laser shock melt injection fine Ce O_2p.Therefore,it not only provides a realization method for the aluminum alloy conductor to play a more environmentally friendly and reliable role in GIS,but also provides technical support for promoting the wider application of fine particle laser shock melting technology.The main work and results of this paper are as follows:（1）Based on the numerical analysis of the temperature field,optimization study of laser shock melt injection fine Ce O_2pinto aluminum alloy was carried out.With the help of Fluent software,a finite element model of A356 aluminum alloy modified by laser shock melt injection fine Ce O_2pwas established,and the temperature field distribution of the molten pool under different laser power and scanning speed was analyzed.Through orthogonal optimization experiment,combining with the characterization of the molten pool defect of the modified layer,better process parameters of laser shock melt injection were obtained.Studies have shown that with the increase of laser power or the decrease of scanning speed,the width and depth of penetration after laser irradiation increase with them.Meanwhile,the more heat accumulated after laser irradition,the longer the molten pool remained liquid;the optimal meltinjection process parameters under the research conditions in this paper are:laser power P=1025 W、scan speed V=0.0067 m/s、defocus D=0 mm。（2）Based on the numerical analysis of flow field,research on microstructure and conductivity of the aluminum alloy that laser shock meltinjection fine Ce O_2pinto was carried out.The flow field model was used to analyze the fluid force and the force mechanism.With the help of SEM,OM,XRD,EDS and other analysis and testing methods,the microstructure,phase composition and strengthening mechanism of the modified layer were analyzed,and the modified material conductivity was measured.Research shows that:Under the synergy of gravity,buoyancy,surface tension and laser impact,the liquid inside the molten pool is fully stirred and strong convection is formed,so that the material structure is more envenly,the active effect of rare earth is fully exerted,the defects of the molten pool are significantly reduced,and the modified zone has a grain boundary structure clear equiaxed and dendritic mixed crystal regions;in addition,without considering the contact resistance and experimental errors,the conductivity of the modified layer has slightly decreased,but it is still within the range of international electrical conductivity requirements.（3）The oxidation resistance and the mechanism of modified layer of aluminum alloy by laser shock injection fine Ce O_2pwere investigated.The constant temperature oxidation behavior of the aluminum alloy fine Ce O_2plaser shock meltinjection modified layer at 160℃was studied,and the oxidation kinetic curve of modified layer was plotted.Based on the results of oxidation experiments and related theories,combined with the comparison of the oxidation surface and the oxidation cross section of the material before and after the modification,the mechanism of oxidation performance change was explored.Studies have shown that the rare earth modified layer is formed in situ by laser impact injection of fine Ce O_2p.The oxidation rate decreases during the oxidation process,and the oxidation increment is significantly reduced,so that the oxidation resistance of the material is significantly improved;at the same time,the pinning effect of rare earth on the alloy further suppresses the oxidation loss.（4）The anti-corrosion performance and mechanism of the aluminum alloy that laser shock melt injection fine Ce O_2pinto was investigated.The electrochemical corrosion behavior of the aluminum alloy fine Ce O_2plaser shock meltinjection modified layer in a 2%H₂SO₄and3%HF mixed solution was studied.The electrochemical corrosion potential,Tafel polarization curve,AC impedance spectra and corrosion were obtained through electrochemical corrosion experiments.The surface corrosion morphology,and its anti-corrosion mechanism was discussed.Studies have shown that the material after the process of laser shock melt injection fine Ce O_2p,due to the introduction of residual stress,reduces the electrochemical activity of the metal atoms on the surface of the material and the internal grain boundary area,and then produces resistance to selective corrosion between the grain boundaries;at the same time,the formation of rare earth hydroxides protects the material,inhibits the corrosion of the material by the corrosive medium,and its corrosion resistance is significantly enhanced.