| The use of AZ31 magnesium alloy to manufacture lightweight components is an important approach to achieve energy saving and emission reduction,but the main problem facing the forming of AZ31 magnesium alloy is the poor forming performance at room temperature.In order to better solve the forming problem of AZ31 magnesium alloy,a new magnesium alloy tube bulge technology has been explored in this paper:thin-walled magnesium alloy tube oil-immersed thermostatic hydraulic bulging technology.The forming principle of this technology is to submerge the mold containing AZ31 magnesium alloy thin-walled tube in dimethyl silicone oil,and then rapidly heat the thermal oil to make the AZ31 magnesium alloy thin-walled tube under the suitable and uniform temperature for hydraulic bulging,and finally obtain the formed parts.The application of this technology can improve theformability of AZ31 magnesium alloy thin-walled tube.ETA/DYNAFORM finite element simulation software was used to numerically simulate the hydraulic bulging process of magnesium alloy thin-walled tube,andto investigate the influence rules of tube forming temperature,required hydraulic pressure,feeding force on both sides and friction on hot oil thermostatic bulging of magnesium alloy thin-walled tube,to obtain the appropriate parameters.Parameters have been set to perform the experiments based on the simulation results.The results show that thin-walled magnesium alloy tube forming parts with excellent performance could be obtained by using the home-made experimental equipment.The main research contents and results of this topic are as follows.(1)The Stress-strain curves of AZ31 magnesium alloy measured by high temperature tensile experiments have been imported into ETA/DYNAFORM finite element simulation software to simulate the thermostatic bulging process of AZ31 magnesium alloy thin-walled tube.(2)A set of experimental apparatus was developed and designed for oil immersion and thermostatic hydraulic bulging of thin-walled magnesium alloy tubes.The experimental device contains heating and temperature compensation system,sealing system,axial feeding system,hydraulic system,hot oil circulation system,and cooling circulation system.The device has high accuracy in controlling the temperature of oilimmersed hydraulic bulging.(3)The optimum process parameters for oil-immersed thermostatic hydraulic bulging of AZ31 magnesium alloy thin-walled tubes with outer diameter(37)23mm,tube thickness of 2mm,and length of 200 mm obtained from simulation and experiments include forming temperature of 200℃,hydraulic pressure of 20 MPa,pushing head force and lubrication.(4)The metallographic microstructure of thermostatic expanded AZ31 magnesium alloy thin-walled tube has been investigated.The results indicate that magnesium alloy tube during the plastic process appears grain refinement phenomenon.The closer to the center of the bulge zone,the more obvious grain uniformity.The size of original coarse grain refines to 4.28μm of that in the secondary bulge zone,and then to 3.98μm in the center of the bulge zone. |
PDF Full Text Request