Warm hydroforming of magnesium alloy tube with large expansion ratio within non-uniform temperature field
(National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China)
Abstract: According to warm hydroforming with poor thickness uniformity and low expansion ratio, a new approach named warm hydroforming with non-uniform temperature field was presented. Warm hydroforming die with nonuniform temperature field was designed and temperature field along tube axis was established with differential temperature gradient. Then, the effect of the temperature difference between the forming zone and the feeding zone on thickness uniformity along the part axis was studied in a certain loading path. Thickening of the feeding zone decreases and the thickness uniformity of tubular part is improved by selecting appropriate temperature difference, for this experiment, suitable temperature difference is 150 °C. Further, the effect of the preform shape formed by warm hydroforming on the limit expansion ratio of magnesium alloy tube was studied, using preform with wrinkles and preform with expansion ratio of 35% hydroformed by using differential temperature. The limit expansion ratio reaches 66.2% by using the preform with expansion ratio of 35%.
Key words: magnesium alloy; warm hydroforming; nonuniform temperature field; limit expansion ratio