Construction And Evolution Of Cellular Automata Model For Microstructure Of Magnesium Alloy

As one of the lightest metal structural materials in practical industrial applications,and due to the advantages of easy processing and recycling,magnesium alloys are widely used in electronics,aerospace,transportation and other fields.It is regarded as the green material for the sustainable development of resources and environment in the 21 st century by the majority of researchers.However,the plastic deformation ability is poor at room temperature and the processing yield is low,which greatly limits the further development of magnesium alloy materials.With the gradual maturity of computer simulation methods,more and more researchers have shifted the focus of material research from the traditional experimental research to the scientific prediction of material properties by using simulation methods,which can play a role in replacing experiments or making up for the deficiencies brought by experimental methods.At present,most researchers are based on the two-dimensional(2D)structure of the material surface or surface features to simulate and research.But from the perspective of the material,the traditional 2D structure information often cannot reflect the three-dimensional(3D)space structure of the material in the real situation.Therefore,it is important to study the internal microstructure of the material through the 3D simulation method.In this paper,the dynamic recrystallization behavior,grain orientation and texture of AZ31 Magnesium Alloy during hot deformation under different deformation conditions were studied by EBSD.The initial microstructure of AZ31 magnesium alloy is equiaxed recrystallized grain with an average grain size of 38?m.And the sample has typical fiber texture before compression test.The larger the deformation temperature,the more fully the degree of recrystallization,and the more uniform the grain structure.The larger the deformation degree or the smaller the strain rate,the greater the recrystallization degree.During the hot deformation process of magnesium alloy,deformation temperature is the biggest factor that determines its dynamic recrystallization mechanism.At 300 ?,the recrystallized grains of AZ31 magnesium alloy nucleate at the original grain boundaries and sub grain boundaries,and the recrystallization behavior is mainly formed by the rotation of the sub grain boundaries,showing typical continuous dynamic recrystallization(CDRX)characteristics.At 400 ?,the orientation of recrystallized grains is deflected during local shear deformation,with 10.41% of large-angle grain boundaries above 80°,and exhibits typical characteristics of rotational dynamic recrystallization(RDRX).During the hot compression process,{1012 } tensile twins are generated.The crystal grains re-rotate the base plane to form a fiber texture with the base plane perpendicular to the compression direction.Based on the thermodynamic conversion mechanism and the principle of energy transition,a 3D CA model of grain growth with orientation numbers was established to simulate the heat preservation process of AZ31 magnesium alloy at temperatures of 300?,380? and 420?.In the process of growth,the grain size increases with the rise of temperature.The angle between the 2D slices of 3D grains is approximately 120°,which is consistent with the traditional 2D CA.By Gauss Amp nonlinear fitting of the grain size,the grain size conforms to the normal distribution,and satisfies the minimum energy criterion for grain evolution.The normal growth of 3D grains meets the Aboav-Weaire equation.At 420? and 2000 cas,the average number of grain planes is between 12 and 14,the maximum number of grain planes is more than 40.The metallographic results show that the relative error of grain size between the experimental and simulated results is within 0.1-0.6?m.In order to predict the dynamic recrystallization behavior of AZ31 Magnesium Alloy during hot compression,the 3D CA theoretical model was established.This model was used to analyze the microstructure evolution under different deformation conditions.The results show that the volume fraction of recrystallization increases with the rise of strain,deformation temperature or the decrease of strain rate.Increasing the strain rate or decreasing the temperature can refine the recrystallized grains.The recrystallization volume fraction was measured by EBSD,and the relative error was between 4.5% and 16.2%.The simulation results agree well with the experimental results.The 3D model can better simulate the recrystallization behavior of AZ31 magnesium alloy during hot deformation.