Research On Microstructure And Properties Of 1060 Pure Aluminum And 6061 Aluminum Alloy Electric Pulse-Assisted Constrained Groove Pressing Sheets

As one of the most commonly used light metal materials,aluminum and aluminum alloys have the advantages of high strength,high toughness,wear resistance,and easy recycling.They are widely used in machinery manufacturing,transportation,and aviation industry.Grain refinement strengthening is an effective way to improve the strength and comprehensive mechanical properties of materials,and Constrained Groove Pressing(CGP)is one of the commonly used techniques for preparing fine-grain.Although high-strength sheets can be prepared by Constrained Groove Pressing,it will cause a decrease in elongation,while the electric pulse-assisted method can effectively improve the strain uniformity and improve the ductility of the deformed sheet.In this paper,the electric pulse-assisted Constrained Groove Pressing(ECGP)of pure aluminum and 6061 aluminum alloy was carried out.The property change and microstructure evolution of the molded sheet were studied,and the influence of pulse current and strain path on the CGP process and the properties of the prepared sheet was explored.(1)The research on Constrained Groove Pressing of pure aluminum plate assisted by electric pulse was carried out.The electric pulse-assisted Constrained Groove Pressing experiment of 1060 pure aluminum plate was carried out at room temperature,and the strength,plasticity and strain uniformity of pure aluminum were improved with the increase of the number of CGP passes.After adding electric pulse,the improvement trend of each performance parameter is basically the same as that of CGP,and the strength of ECGP molded sheet is slightly higher than that of CGP sheet.Under the same CGP pass,ECGP can improve the elongation of the molded sheet more than ordinary CGP,which is increased by 41.3%after one pass and 62.6%after two passes.In addition,the anisotropy and deformability of ECGP were improved after deformation.Metallographic and fracture observation found that the structure of the ECGP molded sheet was more uniform,the dimple depth was higher and the distribution was more uniform,so the ECGP pure aluminum sheet could obtain greater elongation and better strain uniformity.(2)The research on electric pulse-assisted Constrained Groove Pressing of 6061 aluminum alloy was carried out.The 6061 aluminum alloy was subjected to electric pulse-assisted Constrained Groove Pressing with two power-supply methods in the horizontal and vertical directions.It was found that the electric pulse assistance could not increase the number of molding passes,but it could improve the strength,elongation and strain uniformity of the deformed sample at the same time.In the electrochemical corrosion experiments and neutral salt spray weight loss experiments,it was found that the corrosion resistance of the samples after CGP deformation was improved,and the corrosion resistance of the samples was further improved after the addition of electric pulses.(3)The research on the Constrained Groove Pressing mechanism of 6061 aluminum alloy under different strain paths assisted by electric pulses was carried out.The changes of properties and microstructure of 6061 aluminum alloy CGP/ECGP under parallel CGP,CGP-180 and CGP-90 strain conditions were studied.After deformation,the strength is further increased;the strength and elongation of CGP-90 decrease after deformation.The strength and elongation of ECGP-90 were increased by adding electric pulse under the same deformation conditions,especially the elongation of ECGP-90 after deformation increased by as much as 48.3%.Embossing with cross-strain paths reduces the grain size,and electrical pulses further reduce the average grain size.The strain accumulation exceeded a certain level,and the electric pulse released the internal dislocation concentration and transformed them into large-angle grain boundaries.The texture analysis showed that the grain orientation turned to Brass texture along the β and α orientation lines,and the P texture appeared after CGP-90 was deformed.After the addition of pulsed current,the transformation of grains to Cube texture is promoted,which is the main reason for the increase of ECGP plate elongation.