Simulation and experimental research on isothermal forging with semi-closed die and multi-stage-change speed of large AZ80 magnesium alloy support beam

Numerical simulation to optimize the mold structure and forming parameters for a large AZ80 magnesium alloy support beam and experimental formation of the support beam using a 40 MN numerically controlled hydraulic press were carried out. The research results showed that use of a semi-closed mold resulted in full and even deformation of the stair-like support beam forging. Also, the forging could be filled in one step with simple cuboid-shaped billets, thus greatly shortening the forging process. The technique of isothermal forging with a multi-stage-change speed used an ultra-low speed of 0.005 mm/s during the final forming process. The resulting billet was fully softened, which greatly reduced the forming load to less than 40 MN. Die forgings of the large magnesium alloy support beam were thus produced through isothermal forging with a semi-closed die and multi-stage-change speed. Fine and evenly distributed grains were observed for the formed forgings. The longitudinal and transverse tensile strengths of the main strength-bearing part (bottom) were 394 MPa and 398 MPa, respectively; their percentage elongations were 9.6% and 9.8%, respectively. In addition, the forgings were processed into parts and passed a trial loading test before being successfully used in helicopters.