Study On Microstructure Evolution Of AZ61 Magnesium Alloy During Bending Flattening Compound Deformation

Magnesium alloy is a kind of light metal material,which belongs to close packed hexagonal crystal structure.Its few slip system leads to the low plastic deformation ability at room temperature so that the wide use of magnesium alloy is limited.The research goal of this paper is to improve the microstructure and mechanical properties of magnesium alloy materials,improve the plastic forming ability of magnesium alloy materials,and expand the application field of magnesium alloy materials by the method of bending flattening composite deformation.We use numerical simulation and experimental methods to research the change rule of the average grain size of AZ61 magnesium alloy plate in the process of bending flattening composite deformation,and analyze the change rule and influencing factors of mechanical properties and texture strength after composite deformation.In a result,the following research results are obtained:(1)We use DEFORM-3D software to simulate the bending flattening composite deformation process of AZ61 magnesium alloy sheet,analyze the distribution of temperature field and stress field in the deformation area,and optimize the process parameters.In addition,the cellular automata(CA)method was used to simulate the microstructure evolution of magnesium alloy during the bending flattening composite deformation.The simulation results are consistent with the experimental results,and the relative error between them is less than 16.4%.(2)The increase of temperature and the decrease of tooth spacing can promote the dynamic recrystallization of magnesium alloy in the process of bending flattening composite deformation.In this experiment,the grain size is refined from 26.3?m of the initial grain size to 16.3?m,so the grain refinement degree becomes 37.8%.By comparing the average grain size of single bending deformation and bending flattening deformation,we found that the grain refinement degree of bending flattening deformation in this experiment is better than that of single bending deformation.(3)EBSD test technology was used to research the texture distribution of magnesium alloy after composite deformation.It was found that when the deformation temperature was T = 320 ? and the tooth spacing was s = 20 mm,the texture weakening degree of magnesium alloy was the highest,from 16.19 to 10.08,which was 37.7% weaker than the original structure.Through the influence degree of different deformation temperature and tooth spacing on texture weakening,we conclude that in this experiment,the deformation temperature should be controlled at about 320 ?,and the tooth spacing is in the range of s = 15 mm ~ 20 mm in order to have a good texture weakening effect.(4)The room temperature tensile test in RD direction was carried out on the magnesium alloy sheet after composite deformation.The test results indicate that the tensile strength of the original plate,the yield strength and the elongation is,270 Mpa,169Mpa,7.7% to each,while increase to 332 Mpa,215Mpa and 9.8% respectively after composite deformation.Compared with the original sheet,the tensile strength,the yield strength and the elongation are increased by 23%,27% and 27% separately.