| With the application of metal materials in many high-end equipment,the requirements for material performance are becoming higher and higher.The traditional macro level research on materials can not meet the requirements for high performance of materials.Based on this,a series of micro scale finite element analysis methods came into being.Crystal plastic finite element(CPFEM)is one of the effective ways to study the microstructure evolution behavior of materials.Compared with the traditional finite element simulation at the macro level,CPFEM is based on the plastic deformation mechanism of real materials,and can carry out secondary development and Simulation of many materials in real life.Through the study of material constitutive model,crystal internal structure,dislocation slip and other contents,the analysis and regulation of material anisotropy behavior and material microstructure and properties can more accurately simulate the microstructure evolution of materials,realize the scientific prediction of material properties,make up the verification that cannot be realized by experiments,and predict the slip twin mechanism and orientation evolution behavior of materials after deformation.As a non renewable resource,mineral resources play an important role in production.More and more scholars begin to develop new materials to replace traditional industrial metal materials.Taking magnesium alloy as an example,the reserves of magnesite in China account for one third of the global reserves,ranking first in the world.As a new lightweight material with sufficient reserves on earth,magnesium alloy is widely used in transportation industry,medical devices,electronic product manufacturing,aerospace and other fields because of its excellent properties.The research on the preparation,processing and microstructure regulation of magnesium alloy at the micro level is of great significance to realize the wide application of magnesium alloy.The difference of crystal structure determines the difference of independent slip coefficient of materials,and then affects the properties of materials.Magnesium alloy has a close packed hexagonal(HCP)crystal structure,and the number of independent slip systems is small at room temperature,resulting in its weak plastic deformation ability.Based on CPFEM,this paper explores the factors affecting the deformation mechanism of magnesium alloy at room temperature.The following conclusions are drawn:(1)Based on CPFEM,the Voronoi polycrystal geometric model is established in the finite element software,and the model is redeveloped by measuring the initial orientation and elastic-plastic constitutive of magnesium alloy combined with electron backscatter diffraction(EBSD)experiment;The stress-strain curve of magnesium alloy during deformation is measured by compression experiment,and the reliability of the model is verified by fitting with the simulated curve;(2)The annealing temperature and time were respectively set as 280℃×60min、280℃×150min、400℃×60min,and the grain size is 25.3μm、37.2μm、52.6μm,respectively.The model sets the same deformation parameters according to the average grain size of experimental treatment,and analyzes the influence of grain size effect on the mechanical properties of magnesium alloy;(3)Build the same size model and give different initial orientations to the grains to explore the influence of different initial orientations of grains on dislocation slip of magnesium alloy and the interaction between grains with different orientations.In the process of plastic deformation,there are different time and non-uniformity of deformation of each grain,the blocking effect and orientation difference effect of grain boundary between grains,and the compression deformation process will be accompanied by crystal rotation;(4)The difference of grain orientation will lead to the uneven distribution of stress between grains,and different degrees of stress concentration will occur in the interior of the crystal and at the grain boundary.The accumulation of slip dislocation lines on the grain base of AZ31 magnesium alloy in TEM experiment is consistent with the stress concentration in the process of simulated grain slip,and the opening of slip system caused by different orientation grains is different;(5)The model size is set to 0.3mm×0.3mm×0.3mm,and the number of grains and boundaries in the model increases with the grain size,the greater the grain slippage obstacle,and can bear the larger variable.The model strength and plasticity is good,but when the average grain size decreases to 30 m,the influence of the average grain size on the overall plastic deformation process is no longer obvious. |
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