Preparation And Experimental Study Of Forming Limit Diagram Of Magnesium-aluminum Composite Plate At Thermal State

Due to its poor corrosion resistance, the wide application of magnesium alloy is limited. However, aluminum alloy has high corrosion resistance and plastic forming performance. The performance advantages of the two kinds of alloy can be fully exploit by the means of covering a sheet of aluminum alloy on the both sides of magnesium alloy. Scholars in the domestic and overseas only study the forming of clad sheet and its interfacial behavior. The function of after-rolling hot treatment to magnesium-aluminum composite plate and its formability has not been studied yet. Forming limit diagram is the widely used index to characterize the formability of sheet metal which can accurately evaluate the formability of sheet metal. For this reason, warm state forming limit diagram is studied and the relation between formability and forming condition is explained in this paper, which is meaningful to the application of magnesium-aluminum composite plate both in the aspect of theory and in the aspect of engineering application.In this paper, the effect of annealing temperature on interface microstructure, magnesium matrix and mechanical properties at room temperature is studied by hot rolling of magnesium-aluminum composite plate and annealing at the temperature between160℃～340℃. The results show that compound interface become diffusion layer, the thickness of which increases with the increase of the temperature. The twin crystals in the magnesium matrix disappear, equiaxial recrystallized grains appear and grain size first decrease then increase as the temperature increase. The yield strength, tensile strength and yield/tensile ratio of annealed clad sheet decrease and the elongation increase. The best overall properties of clad sheet can be obtained after annealing at200℃and cooling in the air. The elongation after fracture is up to23.9%.Rigid punch bulging device is designed according to the China national standard, which has the function of heating, cooling and measurement of the temperature and is easily handled. The forming limit experiment of heat-treated magnesium-aluminum composite plate is carried out. Then the scatter diagram of forming limit at200℃is acquired. Then the curvilinear forming limit diagram, zonal forming limit diagram and fitting function are acquired after polynomial fitting, and the formability of magnesium-aluminum composite plate at thermal state is well, the forming strain limit under plan strain state is0.277. After comparison between the forming limit diagram of magnesium-aluminum composite plate and that of AZ31magnesium alloy sheet, it can be finally conclude that the forming limit curve of the magnesium-aluminum composite plate is slightly lower than that of AZ31magnesium sheet, and the zonal forming limit diagram is partially coincide, all of which showed that the forming performances of the both are well-matched.