Numerical Simulation And Experiment Research On Rolling Of The AZ31 Magnesium Alloy

Magnesium alloy is regarded as one of the most prospective metallic materials in 21th century due to its low density, high specific strength, high specific stiffness, good damping capacity, excellent shielding properties, and good machinability. Properties of magnesium alloy sheet directly affect stamping properties and product precision, high–quality sheet is critical for qualified products. In my work, numerical simulation and experiment research were conducted. The effect of technical parameters on properties of Magnesium alloy sheet during one-way and cross-rolling was analyzed. The results were shown as follows:(1) Though the numerical simulation, the influence of technical parameters on rolling-stress, thickness displacement, width displacement, sheet shape were studied, the reasonable technical parameters are as following: friction coefficient is 0.3, thickness reduction ratio is 50% in rough rolling, temperature of the sheet is 400℃, roller temperature is between 150℃and 250℃;(2) The relationships among roller temperature, thickness reduction ratio and microstructure were studied in rough rolling experiments. Experiments indicate that the maximum thickness reduction ratio in one pass increases from 40% to 70% by heating the roller to 180℃when the initial temperature of the sheet is 400℃. In the meanwhile , thickness reduction ratio increases from 25% to 67% ,the grain sizes can be decreases from 12μm to 7μ?m.(3) In order to fabricate 0.5mm-thick magnesium alloy AZ31 sheet, two step process rough and fine rolling were adopted. Technical parameters of rough rolling are obtained as following: roller temperature is 180℃, temperature of the sheet is 400℃, thickness reduction ratio is 50%, the fine rolling was conducted as the sheet was reduced to 1mm-thick during rough rolling, technical parameters of fine rolling are obtained as following: temperature of the sheet is 400℃, thickness reduction ratio in one pass is 25%. The refine grain of alloy obtained with an average size about 5μm by heat treatment, the tensile strength is 250MPa, the yield strength is 180MPa, and the elongation is 20%.(4) The rough rolled sheet was further reduced by direct and cross rolling respectively, comparing the effects of rolling method (one way /cross way) on properties of AZ31 magnesium alloy sheet. Compared with one way rolling, the cross rolling process could reduce the anisotropy and yield stress of rolled plate .The ratio of crosswise and the longitudinal elongation in one-way rolling and cross rolling are 0.87 and 0.89, respectively. The yield ratio of one way and cross way are 0.62 and 0.46 at room temperature, respectively.(5) The results showed that the optimum heat treatment condition is 250℃～300℃holding 30 min for AZ31 magnesium alloy sheet.(6) The magnesium alloy AZ31 with RE additive was rolled by the same producing technique. The refine grain of alloy obtained with 5μm～10μm by annealing at 250℃for 30min, the tensile strength can reach 611MPa, the yield strength can reach 377MPa, and the elongation can reach 15.7%.