Effect Of Asymmetric Rolling Processes On Microstructure And Properties Of AZ31 Magnesium Alloy Sheets

Effects of conventional and asymmetric rolling on macroscopic deformation and microstructure of AZ31 magnesium alloy sheet was analyzed in this paper thesis,combined with the finite element simulation method and evolution of the magnesium alloy sheet with external conditions change, comparing advantages and disadvantages of both the rolling processes.With the increase of reduction, asymmetrical rolled magnesium alloy sheet showed signs of edge cracks at thickness 1.0mm. The samples from two processes after annealing to test the mechanical properties of tensile,result showed that tensile strength of conventional rolled magnesium alloy sheet was significantly decreased with temperature rising, the maximum was about 282 MPa, tensile strength of asymmetric rolled magnesium alloy sheet appeared not significant decline with temperature increasing, the maximum was about 310 MPa, but the elongation of that was significantly less than that of conventional rolling. By microscopic observation,asymmetric rolled sheet obtained a significant feature that grain size of big roller side was generally smaller than that of small roller side. Obtained by diffraction experiments, texture of basal surface of big roller side was generally smaller than that of small roller side.Finite element simulation of conventional rolling analyzes stress distribution of conventional rolled element with different reduction, the result showed that rate of reduction increased, deformation degree of elements gradually increased, when reduction came to a constant, deformation degree gradually weakened, and simulation results conformed to experimental results. The impact of stress on tension was observed in three cases from simulation, rolling unit pressure showed a decreased phenomenon with increase in tension, effect of back and front tension is approximately equal to the respective effect of back or front tension alone. Simulation of asymmetric rolling analyzed the impact of speed ratio on element stress and deformation zones, the results indicated that rolling stress exhibited decreased phenomenon with speed ratio increase, but shear stress showed an increased phenomenon. Speed ratio after reaching 2.0, both stresses were almost stable,deformation area approached to be maximized. The simulation showed that rolling specific pressures of surfaces and middle were different, rolling specific pressure and shear stress of layer of slow roll were larger than that of layer of fast roll,the rolling specific pressure and shear stress of middle layer were smallest and equivalent strainwere smallest. The equivalent strain of fast roll surface were smaller than that of slow roll surface,with reduction going on,the three curves of elements were going to be close at last,simulation results conformed to experimental results approximately.