Study On The Microstructure Homogeneity Regulation Of 7050 Aluminum Forging Based On The Cumulative Deformation And Plasticization Of Surface

7XXX aluminum alloy has been widely used in the field of military equipment and aerospace because of its high strength,high toughness,good plasticity,heat treatment,etc.Under the conventional hot-die forging process conditions of the aerospace structural parts,it is difficult to avoid the coarse surface layer of the forgings,which makes the overall organization of the forgings uneven and seriously weakens the service performance of the aerospace structural parts,which usually needs to be completely removed by machining,resulting in a significant reduction in the utilization rate of aerospace materials.Therefore,this paper proposed a new method of regulating the surface plasticization and accumulation of deformation for the uniformity of die forgings,which can regulate the uniformity of 7050 aluminum alloy die forgings by increasing the plasticization and deformation in the surface layer to obtain more accumulation of deformation energy storage and cooperate with the subsequent heat-treatment process.Firstly,the flow stress intrinsic model of 7050 aluminum alloy was established by analyzing and calculating the hot compression experimental data.The accumulated deformation of conventional hot die forging and surface plasticization of 7050 aluminum alloy die forgings were numerically simulated,and the results showed that with the increase of die temperature,the value of surface equivalent variation increased and deformation accumulation occurred.Secondly,through the hot die forging experiment and the surface layer plasticization accumulation deformation experiment of aluminum alloy die forgings,the grain organization evolution law of the surface layer and center of aluminum alloy die forgings under different forming process and solution heat treatment process conditions were analyzed,to clarify the regulation window of the organization uniformity of 7050 aluminum alloy die forgings.Through the mechanical property test and fracture organization observation of forgings,we study the evolution of mechanical properties of aluminum alloy die forgings,and optimize the process parameters for regulating the uniformity of die forging organization.The evolution of dislocation morphology and precipitation phase in the aluminum alloy die-forged parts was observed by transmission electron microscopy,and the microscopic mechanism of the accumulated deformation of superficial plasticization to regulate the homogeneity of the aluminum alloy die-forged parts was revealed.Finally,the TTT and TTP curves of the specimens were obtained by measuring the conductivity and hardness after isothermal quenching.The results showed that the conductivity and hardness of the 7050 aluminum alloy showed an overall increasing and decreasing trend with the increase of holding time at different isothermal holding temperatures,and the nose tip temperature of the TTT and TTP curves was 320°C,where the quenching sensitivity was the best.The specimen’s phase transition kinetic evolution law was analyzed,the phase transition S-curve was obtained,and the phase transition kinetic equation was established to provide a theoretical basis for the microstructure regulation of aluminum alloy die forgings.