Air bending of AZ31 magnesium alloy sheets

Abstract

Authors addressed the case of bending using a press brake, and experimentally investigated and evaluated the effects of various conditions on the bending limit and bending accuracy for an AZ31 magnesium (Mg) alloy sheet (thickness t = 0.5 mm) in air bending. The results indicate that cracks were generated on the surface of the Mg alloy sheet when the bending punch radius was smaller than 1.5 mm (three times of the sheet thickness). To prevent these cracks, warm bending was required, in which the sheet material was heated to 250°C. Also, the amount of springback of Mg was larger than steel when bending at room temperature, since the modulus of elasticity of Mg is smaller than that of steel. However, when the bending temperature was high, the amount of elastic recovery of Mg rapidly decreased, resulted in a significant decrease in springback. When the bending temperature was as high as approximately 300°C, bent products with near-zero springback were obtained. In addition, we quantitatively determined the effect of various bending conditions, such as bending punch radius, die opening and bending temperature, on the bend radius and bend allowance of products. The results provide useful data that can serve as guidelines in actual bending process.