Study On Extrusion 2A12 Aluminum Alloy Hard Anodized Film Of Preparation And Properties

2A12 aluminum alloy formed by extrusion is widely used in aviation industry,but there are many holes on the surface of the substrate,and the internal microstructure and phase corrode seriously along the grain boundary.The oxide film prepared by the existing mature hard anodizing process has low hardness and poor wear resistance,so it is difficult to meet the industrial application.Therefore,it is urgent to develop new hard anodizing process to improve the performance of oxide film.In view of this,the microstructure and micro-morphology of 2A12 aluminum alloy were observed by metallographic microscope and field emission scanning electron microscope,Using energy dispersive spectrometer,microhardness tester,electrochemical workstation and friction and wear tester.to analyze the composition,hardness,corrosion resistance and wear resistance of the oxide film of 2A12 aluminum alloy formed by rolling and extrudsion.And the effects of electrolyte composition,process parameters and pretreatment process?solution temperature?on the properties of extruded 2A12aluminum alloy hard anodic oxide film were studied by single factor test.The main findings are as follows:1.By comparing the microstructure between 2A12 aluminum alloy formed by rolling and extrusion,it is found that the main reasons for the poor oxidation resistance and film properties of extruded 2A12 aluminum alloy are that there are many holes in the extruded 2A12 aluminum alloy,the precipitates are broken seriously,and the anodic oxidation process is easy to ablate.2.The thickness,hardness,roughness,corrosion resistance and wear resistance of the oxide film prepared by single sulfuric acid system and mixed acid system were studied by single factor method.The results show that when the concentration of sulfuric acid,oxalic acid and tartaric acid are 140 g/L,20g/L,30 g/L,the thicknes s,hardness,roughness of oxide film can reach 66±1?m,257±1 HV,0.98?m.Compared with the oxide film obtained in a single sulfuric acid system,the addition of oxalic acid and tartaric acid in the electrolyte can significantly improve the performance of the oxide film.3.Using mixed acid system,when duty cycle is 50%,frequency is 50 HZ,current density is 3 A/dm²,which can obtain the oxide film with thickness,hardness and roughness of 62±1?m,314±1 HV and 1.93?m.4.The effects of different solid solution temperatures?375?,400?,425?,450??on the properties of the oxide film were studied by adding solid solution aging treatment before hard anodizing of 2A12 aluminum alloy.formed by extruded.The results showed that,compared with the sample without solution treatment and after solution treatment at 375?,425?and 450?,the second phase of CuAl₂ inside the material was reduced after solution treatment at 400?.Under these condition,the hardness,thickness and roughness of the oxide film can be reached 385.60 HV,70.59?m and 1.2950?m,compared with the oxide coatings obtained without solution aging,the corrosion potential of the oxide coatings increased by 0.1398 V,the corrosion current density decreased by 0.5501.