Theoretical And Experimental Study Of Deep Drawing Limit Of Magnesia-alumina Composite Plate

The magnesium alloy is characterized by light weight and poor corrosion resistance, yet the aluminum alloy is just the opposite. Covering the two sides of magnesium with aluminum alloy, we can obtain Al/Mg/Al metal composite plate formed by the hot rolling method. The new magnesium-aluminum composite plate with the advantages of light weight of magnesia and corrosion resistance of alumina will be widely applied to the fields of aviation, aerospace, automobile and electronic industry. At present, arduous efforts has been made to the process of deep drawing of magnesium alloy and aluminum alloy, however, as to the magnesium-aluminum composite plate, research still stays on the level of composite method and its influencing factors, and its stamping formability has not been reported.First based on the theory of sheet metal deep drawing, stress-strain distribution of cylindrical parts in deep drawing is analyzed in the paper. Then, according to the risk section strength formula of Whitely, and considering the effect of material properties (characterized by material coefficient A) and plastic strain ratio (r) on the deep drawing limit, a prediction mathematical model suitable to anisotropic materials is derived, which can more comparatively reflect the relationship of stamping performance parameters and deformation degree. Summing up the existing literature, for steel, the value of material coefficient A is1.15.Moreover, hot rolling process of5052/AZ31/5052composite sheet is explored and composite sheet with good bond strength is obtained. Then, uniaxial tensile tests of5052/AZ31/5052heat-treated under various conditions are conducted in order to compare their percentage elongation, grain size and interfacial brittle phase. By this way, the best heat treatment process is optimized and sheet metal with good stamping performance is obtained.By virtue of uniaxial tensile tests, plastic strain ratio r of5052/AZ31/5052composite sheet is determined, whose values under room temperature and120℃are respectively2.369and1.450, and values of strain hardening index n under room temperature and120℃are respectively0.167and0.121.According to GB12825.3-2008, a set of deep drawing experimental device with the function of self-rating blank holder strength and respective temperature control and measurement for punch and die is designed, on which deep drawing forming experiments of5052/AZ31/5052composite sheet and AZ31are conducted. The limit drawing coefficients of them at room temperature are0.758and0.781, and at120℃are0.625and0.667, so the deep drawing performance of composite sheet is better than that of AZ31. Comparing the limit drawing coefficients determined by deep drawing experiments and the calculated ones from prediction mathematical model, we can conclude that the material coefficient A of5052/AZ31/5052composite sheet and AZ31is2.2at room temperature.