Curvature, Microstructure And Mechanical Properties Of Aluminum Sheets Processed By Snake Rolling

Abstract:Snake rolling is a new type of rolling processing technology which developed in these years. Compared to other asymmetric rolling, snake rolling has two asymmetric parameters which are horizontal-roll-displacement (⊿) and velocity ratio(ωu/ω1). Studies have shown that snake rolling has the advantage of overcoming the plate bending. It can also increase shear deformation in the sheets, and thus impact the microstructure and mechanical properties of the sheets. The effect of rolling parameters on curvature during snake rolling is unclear. Also, there is a lack of researches on the microstructure and mechanical properties of snake rolled straight sheets.In this study, AA7050and AA1060aluminum alloys were taken as the research materials. First, the effect of the rolling parameters (reduction (r),⊿and ωu/ω1) on plate curvatures during snake rolling was researched, and parameters to control the curvature of the rolled sheets to obtain straight rolled sheets were identified. Second, with the aid of optical microscopy, X-ray diffraction, Scanning electron microscopy, tensile machine and micro-hardness tester, the microstructure and mechanical properties of snake rolled straight sheets were investigated, and the results were compared with the symmetric rolled sheets. The conclusions can be summarized as follows:(1) The sheet curvature was effected by the r、⊿and ωu/ω1.When the r and⊿were fixed, the absolute value of the curvature decreased firstly and then increased with the increase of ωu/ω1, and the sheet was trend to bending to the faster roll. At the same time, the bending direction of the sheet was changed,. Straight sheets were obtained in the snake rolling process when suitable parameters were chosen for each reduction.(2) The test of the insert pin in the two materials revealed that there was more shear deformation taking place at the middle layer of the snake rolled sheet, and the shear deformation under the same direction was increased throughout the thickness in magnitude. Compared to AA7050, the distribution of the shear deformation throughout the thickness is more uniform in AA1060aluminum.(3) The results of the microstructure and mechanical properties of the AA7050straight sheet showed that:the average grain size of the snake rolled sample was smaller than that of its counterpart from symmetric rolling. The textures of the upper and lower layers are close to the shear texture, while those of the other layers are rolling textures. The hardness values of the snake rolled samples in all conditions were slightly higher than the symmetric rolled samples, and the hardness was higher with a larger⊿. The strength of the snake rolled samples was slightly higher than the symmetric rolled samples, but the plasticity was nearly the same.(4) The result of the microstructure and mechanical properties of the AA1060straight sheet showed that:the grain structure of the snake rolled sample was distributed more uniform than that of the symmetric rolled sample, and there were more high-angle grain boundaries in the snake rolled sample. The hardness values of the snake rolled sample in all conditions were slightly higher than those of symmetric rolling, and the uniformity was improved. The hardness was higher with a larger⊿. Compared to symmetric rolling, snake rolling led to a slightly higher strength than symmetric rolling, but the plasticity was nearly the same.