The Research On Rolling Forming Of AE42 Magnesium Alloy

Magnesium alloy has been widely used as structural components in the aerospace, electronics, and automobile industry. Wide application of magnesium alloy sheets is limited by the immature magnesium alloy plate manufacturing technology at present. In this study, AE42 magnesium alloy were used as the starting materials to study the hot compression and rolling behavior.In this paper, the microstructure and mechanical properties of as-cast AE42 magnesium alloy were studied with OM、SEM and X-ray deflection. The results show that the microstructure of as-cast AE42 magnesium alloy is consisted of primaryα-Mg phase, Al11RE3 and Al2 RE phase. The Al11RE3(or Al4RE)phase is body-centered orthorhombic which is block-shaped、short rod-like and needle-shaped phrase. These phrases distribute by or across the grain boundary. And the Al2 RE phase is laves crystal which is granulal phrase, these phrases disperses in grain boundary and in the interior of the grain. Mechanical properties at room temperature of as-cast AE42 magnesium alloy is not high, tensile strength, yield strength and elongation are117.6MPa, 53.2MPa and 10.87, respectively, the fracture mode presents the characteristics of brittle fracture.The homogenized was carried out at 400 ℃for 12 h, and then hot compression tests was conducted on the Gleeble-3500 hot simulator. The results shown that the flow stress increase with the decrease of deformation temperature or the increase of strain rate. The deformation process can be divided into three stages: work hardening,the stress softening stages and stages of dynamic balance. In present study, it was found that the hyperbolic sine law can be applied at general stress.Microstructure observations of the AE42 magnesium alloy after hot compression showed that the evolution of the microstructure was closely related to deformation temperature and strain rate. It was found that the microstructure of the AE42 magnesium alloy after compression has twinning, DRX and both mixed. When the strain rate is constant, as the temperature increases, twin gradually decreases andeventually disappears, recrystallization grains gradually increase, and the grain size is higher than before. When deformation temperature is constant, with the increasing of strain rate, the recrystallization gradually increased, grain size refinement, some of deformation grain is elongated along 45 ° direction, and then the twin is appeared.The stain of 0.5 is used to establish the processing map. From the processing map can be obtained: The domain of stability can be divided into two areas: 1)350-450°C/0.001s-1-0.5s-1, the maximum power dissipation efficiency value is 28%,which represents completely DRX; 2) 275-375°C/0.001s-1-0.1s-1, the maximum power dissipation efficiency value is 18%, which represents partly DRX. And the power dissipation efficiency value increases with increasing degree of DRX and grain size. The maps exhibit a domain of adiabatic shear bands and matrix cracking occurring at 250-450°C/1s-1-10s-1 which should be avoided in plastic deformation.According to the processing map and the actual production, the range of rolling parameters of AE42 magnesium alloy can be assured, and the change of microstructure, texture and mechanical properties can be analyzed by the rolling deformation, rolling temperature, rolling passes and rolling direction. It concluded that the rolling deformation, temperature and pass have a great influence on microstructure and the quality of alloy plate. The surface quality of rolling plate can be improved by increasing rolling pass or rolling temperature. With the increase of rolling deformation, rolling temperature and rolling pass, the number of twins are decreased, the range of dynamic recrystallization is gradually increased, the recrystallized grain size increases with the rise of rolling temperature.Texture evolution of AE42 magnesium alloy was studied by X-ray diffract meter,It formed strong {0002} after rolling and showed obvious anisotropy of magnesium alloy plates. The mechanical properties are seriously affected by microstructure and texture at room temperature. The texture strength is weakened with increase of rolling pass and with the increase of rolling temperature; texture strength increases first and then decreases. And the uniform and fine equiaxed grains can be formed by changing the direction of the rolling direction, which can significantly weak the basal texture strength reduce the anisotropic plate and improve the plastic deformation of AE42 magnesium alloy.According to macro morphology, microstructure, texture and mechanical properties of AE42 magnesium alloy after rolling, assured the optimized rolling parameters as follows: rolling deformation: 75%, rolling temperature: 450 ℃, rolling pass: 8 times. For this condition, the tensile strength, yield strength and elongation is235.57 MPa, 140.11 MPa and 16.08%, respectively, compared with the as-cast increased by 97%, 156% and 39%, respectively.