Construction Of Equivalent Strain Distribution Model For 7050 Aluminum Alloy Forging And Regulation Of Microstructure Uniformity

As a typical ultra-high strength lightweight alloy,7XXX series aluminum alloy is widely used in the aviation field.The typical section of thin-walled aluminum alloy structural parts is H-shaped.However,due to the conventional hot forging process,there are often large differences in the microstructure properties of the surface and the core,leading to the reduction of mechanical properties,service life and material utilization rate during service.In order to improve the microstructure uniformity of aluminum alloy H-shaped forging,the surface plasticizing cumulative deformation process was proposed in this paper.Combined with the subsequent heat treatment process,the deformation energy storage of the surface layer of forging was improved by enhancing the plastic deformation capacity of the surface layer.By analyzing the transformation law of the microstructure of forgings during deformation and heat treatment,the microscopic mechanism of surface plasticizing cumulative deformation process to improve the microstructure uniformity was revealed.Firstly,DEFORM finite element analysis software was used to simulate the forming process of surface plastic-cumulated deformation process,explore the equivalent strain distribution law of forgings,and analyze the reasons affecting the microstructure uniformity of forgings.Based on the response surface method,the equivalent strain distribution model was established,and the accuracy of the model was verified,and the deformation uniformity analysis model was constructed using the evaluation function of deformation uniformity as the media.Secondly,the microstructure evolution of the surface and core of aluminum alloy forging under different forming process and heat treatment conditions was analyzed by metallographic experiments.The results show that by the surface plasticizing cumulative deformation process,the initial grain size of 3～4 forging is refined to 6～7,and the corresponding grain size is reduced from 105μm on the surface and 83μm in the core to37.93μm on the surface and 39.84μm in the core,reaching the fine grain range,and achieving the surface plasticizing cumulative deformation control for the uniformity of microstructure.Finally,the evolution law of grain boundaries and grain orientation of H-shaped forgings was characterized and analyzed by scanning electron microscope,and the evolution mechanism of microstructure of forgings was clarified.The results show that the dynamic recovery of microstructure occurs during the cumulative deformation of surface plasticizing,and the increase of temperature effectively increases the dislocation density and deformation energy storage of forgings.With the increase of solution time,the static recrystallization of microstructure of surface and heart of forgings results in the decrease of dislocation density and deformation energy storage.The local mean orientation difference data were used to calculate dislocation density and deformation energy storage.It was found that when the temperature was 310℃ and the solid solution time was 45 min,the dislocation density difference of the surface and the heart of the forging was the smallest,and the deformation energy storage was 16.57J/mol and 15.50J/mol,respectively.By analyzing the evolution law of microstructure and deformation energy storage of forging,the theoretical basis is provided for the regulation of microstructure uniformity of aluminum alloy forging.