Additive Manufacturing AlSi10Mg Investigation Of Electrochemical Polishing Process

At present,Al Si10Mg(ASM)alloy is the most widely used Aluminum-silicon alloys in additive manufacturing.ASM alloy has the advantages of good fluidity,weldability and low shrinkage rate,which is conducive to additive manufacturing.However,due to the technical limitations of additive manufacturing technology(powder adhesion,porosity and molten pool effect,etc.),the workpiece surface roughness is large,which is difficult to meet the requirements of high precision.Therefore,it is necessary to cooperate with subsequent surface finishing measures to improve the surface quality of the workpiece.In this paper,electrochemical surface finishing of ASM alloy produced by additive manufacturing is studied by electrochemical polishing process.The surface finishing of ASM alloy has been studied by some scholars,but most of them adopt mechanical polishing methods,such as grinding and sandblasting.It is seldom explored by electropolishing.Therefore,exploratory electropolishing experiments were carried out for the heat-treated and shaping samples of ASM alloy manufactured by additive.The initial roughness of the heat-treated and shaping workpiece is reduced from 8?12?m and 3?5?m respectively to about 2?m.Firstly,according to the surface characteristics of ASM,the pretreatment process of workpiece is studied and discussed.At room temperature,the volume ratio of HNO₃:HF:H₂O=10:3:7(analytical pure)is the suitable pickling solution for ASM alloy,and the optimal pickling time for heat-treated and shaping workpiece is 20 s and 50 s,respectively.In addition,the action mechanism of acid pickling on the surface of the sample is investigated:during the pickling process,the Al phase on the surface is further oxidized to form a layer of Al₂O₃ film,and the content of Si element decreased.Therefore,we conclude that pickling pretreatment is necessary.In the electropolishing experiments of two kinds of workpieces,it is found that the electrolyte of acid system is not suitable for ASM alloy.By using LSV variable voltage method,when the magnetic thermostatic agitator rotating speed is 4 r/s,the electrolyte temperature is 40?,the Na OH and EDTA concentrations are 60 g/L and 16.7 g/L,respectively,the heat treatment samples get a good polishing effect.By using the constant voltage method,the shaping workpiece can be polished well when the voltage is 3 V,the speed of magnetic thermostatic stirrer is 4 r/s,the temperature of electrolyte is 40?,the Na OH and Na F concentrations are 60 g/L and 33.4 g/L,respectively.When the voltage is reduced to 2 V,the shaping workpiece with a roughness of about 2?m can be obtained stably by the secondary constant pressure polishing.Follow-up tests show that the two samples are not only improved in brightness and roughness,but also improved in corrosion resistance.Therefore,electrolytic polishing technology not only helps to finish the surface of ASM alloy,but also has a wider application space for additive metal manufacturing.