The formability of light-weight alloy, such as aluminum alloy, magnesium alloy, can be improved significantly when formed at elevated temperature. Superplastic forming (SPF) is a well-known manufacturing method to form complex part of these materials. In order to realize mass production of SPF in industry, forming at high strain rate should be realized. In this study, the mechanical properties of 5A06 sheet were tested by uniaxial tensile test at high strain rate and elevated temperatures up to 550 ℃. Free bulging test and forming of round cup were carried out to evaluate the formability of the 5A06 sheet. Results show that the total elongation of the 5A06 sheet began to increase rapidly after 200 ℃, and reached the maximum value at 450 ℃. At higher temperature, early brittle fracture occurred. In free bulging test, the bulging height remained almost constant about 27.0 mm, which means the formability of the sheet is not sensitive to forming temperature at elevated temperature. In the forming of round cup part, temperature has direct effect on the corner filling ability of the sheet, especially at temperature lower than 400 ℃.
He Zhubin, Fan Xiaobo, Xu Yongchao, Yuan Shijian Harbin Institute of Technology, Harbin 150001, China
Ring hoop tension test and tube bulging test were carried out at elevated temperatures up to 480 ℃to evaluate the formability of AZ31B extruded tube for internal high pressure forming （IHPF） process. The total elongation along hoop direction and the maximum expansion ratio （MER） of the tube were obtained. The fracture surface after bursting was also analyzed. The results show that the total elongation along hoop direction and the MER value have a similar changing tendency as the testing temperature increases, which is quite different from the total elongation along axial direction. Both the total elongation along hoop direction and the MER value increase to a peak value at about 160 ℃. After that, they begin to decrease quickly until a certain rebounding temperature is reached. From the rebounding temperature, they begin to increase rapidly again. Burnt structure appears on the fracture surface when tested at temperatures higher than 420 ℃. Therefore, the forming temperature of the tested tube should be lower than 420 ℃, even though bigger formability can be achieved at higher temperature.
