Deformation Limit Of Hydroforming Of AZ31 Magnesium Alloy Tubes At Elevated Temperature

Hydroforming of magnesium alloy tubes at elevated temperature is an advanced manufacturing technology in both light material and lightweight structure product. The research on warm hydroforming of magnesium alloy tubes is highly significant.The mechanical properties of AZ31 magnesium alloy tubes were investigated by tensile tests at different temperatures from room temperature to 350℃. It was found that the yield stress and the maximum stress decrease with increasing temperature and the ductility increases very rapidly with increasing temperature. The results show that mechanical properties of AZ31 magnesium alloy tubes are decided by temperature.Tubes hydroforming limit theory and hydroforming plastic instability criterion were researched. Plastic instability criterion and Hill new yield criterion were also used to predict the Forming Limit Diagrams and study the influence of material properties on FLD.Warm hydroforming of AZ31 magnesium alloy tubes were simulated by a 3D simulation software, Dynaform. In the simulation, the influence of temperature and the length of bulging section on tube wall thickness distribution and forming limit were researched and the length of tubes bulging section standing for different strain were confirmed. According to this an experimental system were designed to study warm hydroforming of AZ31 magnesium alloy tubes at elevated temperatures.Warm hydroforming experiments of AZ31 magnesium alloy tubes at different temperatures from room temperature and 250℃were carried out to study diversification trend of tube fracture pressure and bulging rate. The simple FLD at different temperature was built and the influence of temperature on bulging rate and FLD was studied. At last, experimental results were analyzed from material microcosmic structure.