Simulation And Experimental Research On Isothermal Semi-Closed Die Forging Of Magnesium Support Beam

Since the wrought magnesium alloys has a series of excellent characteristics, such as low density, high specific strength, specific rigidity, and excellent seismic resistance property, which has become the important structural materials of aerospace components manufacture. However, magnesium alloy performs extremely sensitive to deformation temperature and deformation rate in the process of plastic deformation, leading to conventional deformation process is easy to cause the brittle rupture problem. Based on the analysis of the structure characteristics and the material demands for AZ80wrought magnesium alloy of the support beam parts, a isothermal semi-closed die forging process for producing magnesium support beam was put forward in this paper, and the isothermal semi-closed die forging process theoretical and experimental research was carried out, made the following results:(1) Based on the structure of the magnesium support beam parts, a ladder-type structure forgings was designed, the influence of the different structure die-open structure die with parting face along the outer contour and semi-closed structure die with the parting face along the upper surface-on the rheological properties of the support beam forging was analyzed. The results show that:compared to the open structure die, the die forging magnesium support beam produced by the semi-closed structure mould has significant advantages:the deformation is fuller and more uniform; the flash is less, improved material utilization, the forging stock volume reduced4.7%; the forging billet shape is simple cuboid which obtained through free forging, improved production efficiency.(2) The influence of the forging process parameters on rheological behavior of the support beam forging was studied by simulation software Deform-3D. The results show that:when the mold temperature is raised to the isothermal forging process of380℃, the plasticity of the magnesium support beam performs well, the forgings temperature and effective strain distributed uniformly, and the load is low; when the forming speed is reduced to0.1mm/s, the deformation temperature rising is small and distributes uniformly, and the load is low for the forgings stock fully softened; when the friction coefficient is reduced, the forging load decreased and the uniformity of the effective strain distribution improved; when the variable-velocity isothermal forging technology is adopted, the forging load reduced significantly, the deformation uniformity and forging efficiency improved.(3) The forging process experiment of the magnesium support beam was carried out on the4000tons of NC isothermal forging hydraulic press. The die forgings of magnesium support beam without crack was developed, and the support beam’s stable batch production process documents was formed, which shows that the design of forgings and the isothermal forging process can effectively solve the problem that magnesium alloy is easy to crack during the process of plastic deformation. Semi-closed isothermal forging process can significantly improve material utilization and shorten the forging process.(4) The magnesium support beam forgings micro structure analysis and mechanical performance test was carried out, the results show that: the smaller the forging grain size, the higher the tensile strength; the average grain size is small in the deformation fully part, on the bottom point, a small homogeneous recrystallization microstructure was obtained when the effective strain reached0.912. The bottom of the support beam is the main bearing parts. The longitudinal tensile strength of the bottom is394MPa, long transverse tensile strength of the bottom is398MPa, and the high direction tensile strength of the bottom is348MPa. Mechanical performance is good, which has passed the load start-up test and successfully applied into a helicopter.