The Effect Of Composite Rolling Process On The Composition, Microstructure And Properties Of The Metallurgical Bonding Of Al And Mg

There are many advantages of employing magnesium alloys as structural materials, including low density, high strength, good thermal conductivity, good vibration damping and impact resistance. However, poor corrosion resistance, a major disadvantage of magnesium alloys has greatly limited their application in various fields. By contrast, pure aluminum has good anti-corrosion property, and therefore, in this study, pure aluminum and AZ31magnesium alloy were combined to make magnesium-aluminum composite plate by high temperature rolling, which will have a good surface corrosion resistant like aluminum and an excellent specific strength like magnesium. Such a composite plate can find its applications in many industrial areas, such as automobile and aerospace, to provide lightweighted products to save energy and to reduce emission.This paper studied the effect of hot rolling temperature and the processing parameters of the following annealing on the binding strength of the magnesium-aluminum composite plate. Metallographic microscope, scanning electron microscopy, electronic universal tensile machine and other equipment were used to test the composite plate. It was found that the highest interface binding strength of the magnesium-aluminum composite plate is obtained at the rolling temperature of400℃, reduction of50%and annealing at300℃for2hours. Laminated intermetallic compounds of A12Mg17(adjacent to Mg metal) and Al3Mg2.(adjacent to Al metal) were found at the interface. The intermetallic compounds may have a significant effect on the bonding properties of the composite plate.The effect of the Zn film inserted between AZ31and Al interfacial on the bonding strength was also studied. It was found that two intermetallic compunds were formed due to the presence of the Zn film, one is ZnAl adjacent to the Al metal and the other is MgZn2adjacent to Mg metal. Oversized ZnAl layer and MgZn2layer was not conducive combination of composite plate. During the annealing process, the intermetallic compound dimensions unchanged. But due to diffusion, Zn atoms formed a certain degree in Al which can play a role in solid solution strengthening. The optimum rolling conditions for the magnesium-aluminum composite plate with a Zn film insertion are rolling temperature of300℃, reduction of50%and annealing at300℃for3hours. With this condition, a binding strength of16MPa can be achieved. At400℃rolling, however, Zn film was melted and transient liquid phase diffusion occurred to produce a Mg/Zn/Al ternary phase and Mg/Zn binary phase at the interface. The Mg/Zn/Al ternary phase may weaken the composite interfacial binding strength of the composite plate.