Strong Multidirectional Strain-hardening Numerical Simulation And Experimental Analysis Of Deformation Process Of Aluminum Alloy

7075 aluminum alloy is a kind of high strength aluminum alloy,which is widely used in industry.However,its plasticity is relatively low,in order to improve its mechanical properties,the internal grain can be refined by strong plastic deformation and aging method,which can improve both strength and plasticity.As one of the representative processes of the strong plastic deformation method,the multi-direction forging technology is to make the forgings undergo large plastic deformation and refine their grain by repeatedly pulling up the pier in multiple directions and accumulating large strain.In this paper,the effect of the unmeasured parameters on the strength and plasticity of forgings in multi-direction forging process is studied by the method of numerical simulation and experiment.Mainly carry out the following tasks:(1)Taking 7075 aluminum alloy as the research object,thermodynamic simulation and multidirectional forging experiment were conducted,the true stress-true strain curve based on different strain rates at different temperatures was obtained by means of thermodynamic simulation experiment,then according to the curve and microstructure image,linear regression and calculation were conducted.The constitutive equation of high-temperature rheological stress and dynamic recrystallization mechanical model of 7075 aluminum alloy were obtained,then DEFORM-3D software was used to simulate the multi-direction forging process of 7075 aluminum alloy.The maximum grain size of forgings after four passes is 20.8 microns and the minimum grain size is 0.106 microns,and the volume fraction of dynamic recrystallization is up to 1.75%.(2)The thermal compression test was simulated with deform-3 d software,and the effects of deformation,temperature and compression speed on dynamic recrystallization and average grain size of forgings were analyzed.It provides a theoretical basis for promoting the development of forging technology of 7075 aluminum alloy.(3)Each.parameter in the two-dimensional dynamic recrystallization model based on cellular automata was obtained by linear regression.The Microstructure of the post-processing module of DEFORM-3D was simulated by cellular automata.The minimum grain size is 1.12micron,the maximum grain size is 22,45 microns and the average grain size is 6.813 microns.(4)Electron backscatter diffraction(EBSD)and metallographic experiments were carried out on the original,forged and aged samples of 7075 aluminum alloy.The maximum grain size of the forgings obtained after forging is 28 microns and the minimum grain size is 2.5 microns.According to statistics,the average grain size is about 6.57microns and the volume percentage of dynamic recrystallization is 1.28%.The tensile strength before and after forging and after aging treatment were 555.74mpa,648.73mpa and 667.34mpa,through the normal temperature tensile test.The accuracy of the dynamic recrystallization model was detennined by comparing the results of EBSD experiment and simulation.