Study On The Severe Plastic Deformation Technology Of Alternate Ring-Groove Pressing And Torsion For 5083 Aluminum Alloy

5083 aluminum alloy is a medium-strength Al-Mg series aluminum alloy.Among the non-heat treatable aluminum alloy series,it has good toughness and corrosion resistance,as well as excellent machinability and weldability.It has been widely used in aerospace and automotive industries.The strength and toughness of 5083 alloy is the main problem that restricts its application,so the recent hot spot lies on improving the strength and toughness of 5083 alloy.One of the ways to improve the mechanical properties of metals is to refine the grains(nano or submicron).The reduction of grain size will improve the strength and toughness of materials at room temperature,and may also obtain good formability and superplasticity.Severe plastic deformation(SPD)is a well developed grain refinement process.However,due to the introduction of large strain in the deformation process,although the material strength is improved,the plastic elongation of the material is often seriously reduced,which has become the bottleneck restricting its wide development and application.In this paper,a new severe deformation process method to greatly improve the strength and elongation of aluminum alloy plate is proposed through the coupling and synergy of multiple factors such as repeated tension compression cyclic stress state,torsional shear severe plastic deformation and warm thermal dynamic recrystallization.The severe plastic deformation process of alternate ring-groove pressing and torsion is established to realize the coordinated control of tension,compression and torsion and the coupling control with temperature in the process of severe plastic deformation.The material physical mechanism of greatly improving the comprehensive mechanical properties of plates prepared by the process of alternate ring-groove pressing and torsion under cyclic stress-strain deformation is deeply analyzed.The tensile mechanical properties of 5083 aluminum alloy sheet from room temperature to 300 ℃ were studied,the real tensile stress-strain curves at different temperatures were obtained,and the metallographic structure and fracture morphology were analyzed,which provided a basis for process simulation and performance comparison.Two new severe plastic deformation processes,alternate ring-groove pressing and alternate ring-groove pressing and torsion under cyclic stress state,are proposed.The process flow of severe plastic deformation process of alternate ring-groove pressing and severe plastic deformation process of alternate ring-groove pressing and torsion are established,the mold structure of alternate ring-groove pressing is designed,the mold is optimized by Abaqus-Isigh joint simulation,and the primary and secondary relationship between the peak strain of the plate after alternate ring-groove pressing of the two sets of dies is determined,According to the primary and secondary relationship and the common interval of each solution objective,the solution space of the optimal solution of wave height is determined,and finally the optimized mold size is obtained to make the formed sheet meet the requirements of uniform deformation.The finite element simulation of severe plastic deformation process of alternate ringgroove pressing and torsion is carried out,the stress-strain distribution and coordination relationship in the process of alternate ring-groove pressing and torsion are analyzed,and the influence law of cyclic stress state on material strain accumulation is analyzed.The effect of radial stress,radial strain and thick strain at the center of circular plate is in the cyclic state of tension and compression,and in the cyclic deformation state of continuous tension and compression;Due to the deviation of other areas of plate deformation from the torsion center,the shear deformation occurs obviously in the process of flattening,and the plate deformation process is in the state of repeated cyclic deformation of tension compression torsion shear.The test mold was designed and manufactured,and the process test was carried out with the self-developed tooling.The coordinated control of tension,compression and torsion in the whole process was realized,and the large-size flat plate samples were successfully prepared.The microstructure and properties of processed plates under different process conditions were analyzed and tested,and the effects of cyclic stress and severe plastic deformation on the microstructure and properties of materials were studied.Under appropriate process conditions,the mechanical properties of the plate treated by alternate ring-groove pressing and torsion process are significantly improved.The mechanical properties of the plate treated at 300 ℃ for one pass are the best,and the strength and plastic elongation are greatly improved.Compared with the original plate,the yield strength,tensile strength and fracture elongation are increased by 68.2%,26.4% and67.5%,At the same time,it also exceeds the highest mechanical properties of the plate prepared by repeated molding and warm flattening.The main physical mechanism of increasing the strength and elongation of process of alternate ring-groove pressing and process of alternate ring-groove pressing and torsion is proposed,that is,the initial dynamic recrystallization sub grain boundary network strengthening and toughening mechanism of cyclic strain(IDRNS mechanism,initial dynamic recrystallization network stitching).The strengthening mechanism of the second phase is explained and verified by HRTEM experiment.The development law of dynamic recrystallization structure under severe deformation is obtained.The evolution law of texture in the process of severe plastic deformation under cyclic stress is analyzed and obtained by EBSD technology,and the influence law of both on mechanical properties is analyzed.