Transverse Microstructural Evolution And Its Cellular Automata Simulation During Hot Rolling Of AZ31 Alloy Wide-width Plate

Wide width magnesium alloy sheet is an important material choice for large parts(such as automobile panel and body panel)to realize structural lightweight.The key to breaking through its large-scale application is to realize the mass production of high-quality sheet with a width of more than 1500 mm.Flat ingot casting rolling is the most economical and efficient method to produce wide width magnesium alloy sheet at present.During rolling deformation,the temperature and stress distribution in the wide direction are not uniform,and will become more significant with the increase of width.Affected by the HCP crystal structure,the microstructure evolution mechanism of magnesium alloy is highly sensitive to the stress and temperature state,resulting in obvious differences in the wide structure distribution of 1500 mm wide plate,which seriously affects the mechanical properties and secondary formability of the plate.However,for industrial 1500 mm wide magnesium alloy plate,there is little research on the distribution law of wide physical field and the microstructure evolution mechanism under the influence of hot rolling,especially the correlation between deformation conditions and wide microstructure is not clear,which affects the efficient and high-quality rolling production of wide magnesium alloy plate.Therefore,based on the characteristics of hot deformation and microstructure evolution of magnesium alloy,combined with finite element simulation of rolling process,experimental analysis of hot rolling microstructure and CA modeling of microstructure evolution,this paper qualitatively and quantitatively studies the microstructure morphology,grain size characteristics and recrystallization state of 1500 mm wide magnesium alloy plate after one pass and two passes rolling respectively.A series of simulation conditions and CA model parameters that can accurately predict the microstructure evolution of the rolling process are defined,and their reliability is verified,which provides a theoretical basis for the prediction of microstructure and properties and process pre adjustment in the industrial rolling production of wide width magnesium alloy plate.(1)The mechanism of hardness,microstructure and dynamic distribution of magnesium alloy under different rolling width and rolling pass width of 13 mm were analyzed,and the effects of different rolling pass width and rolling pass width on the tensile strength and recrystallization of magnesium alloy were obtained.(2)Combined with the finite element analysis method,by analyzing the wide-range temperature distribution and equivalent stress-strain distribution of wide-range magnesium alloy plate from R1 zone to R6 zone,the wide-range distribution law of wide-range magnesium alloy plate in the rolling process is revealed,which provides deformation conditions for the subsequent CA simulation in each region,and prepares for the cross-scale combination of finite element cellular automata method.(3)Based on the thermodynamics and energy dissipation mechanism of real grain growth,the corresponding cell transformation rules are formulated according to the microstructure experimental data,so as to establish the grain growth model and generate the high-precision metallographic structure of 13 mm thick plate,which lays a foundation for further establishing the dynamic recrystallization CA model in the process of plate rolling.(4)The experimental magnesium alloy material parameters were accurately obtained by reversible method,and the dynamic recrystallization CA model of wide magnesium alloy plate during one pass rolling was constructed.The nucleation activation energy and hardening index were obtained as 1580 MPa.The microstructure of wide magnesium alloy plate after rolling was simulated by combining finite element method with cellular automata method,and the overall distribution law of wide microstructure after one pass rolling was studied,Further using the established high-precision model to simulate the second pass rolling of plate,it is found that it still has a certain adaptability.