| In this paper, the plates of Mg/Al layer composites were fabricated by casting-rolling bonding technique, in order to explore a new method to fabricate Al/Mg bimetal composites and strengthen the interface combination by hot rolling, also to improve hot rolling bonding yield rate and to broaden the preparation technology of Al/Mg bimetal layer composites. The preparation technology of as-cast Al/Mg bimetal composite ingots and its rolling performance have been studied. The effect of casting and heat treatment on microstructure at the bonding interface of Al/Mg composite ingots were investigated, and then the evolution of microstructure and interface bonding properties on Al/Mg composite after hot rolling and annealing have been studied by using of OM, SEM, EDS and XRD, etc. The results showed that:1. The best parameters of Al/Mg bimetal composites prepared by casting bonding are as follows,1) The1060pure aluminum boxes were produced by argon arc welding processing, the mural thickness of the box is1-3mm which is10～20percent of the composite ingot, The ingots of Al/Mg composite were prepared by pouring molten magnesium alloy into the box of1060pure aluminum using gas protection method at660～700℃.2. As-cast AZ31magnesium alloy showed a typical non-equilibrium cast structure consisting mainly of a-Mg matrix and eutectic which consisted of a-Mg and β-Mg17Al12phases. A diffusion fusion layer is formed in the interface of1060/AZ31composite ingot, which is composed of a-Mg solid solution, eutectic and the Mg-Al inter-metallic compounds such as β-Mg17Al12and AlMg layer that a complex metallurgical interface was formed.As-cast Mg-2.0Mn-0.6Ca alloys consisting mainly of a-Mg matrix, and some granular B-Mn phases which distributed in the a-Mg matrix and grain boundaries. In addition, there were trace of eutectics which consisted of a-Mg and Mg2Ca phases distributed along the grain boundaries. A diffusion fusion layer is formed on the interface of as-cast1060/Mg-2.0Mn-0.6Ca composite plate, which is composed of a-Mg solid solution, eutectic and the Mg-Al inter-metallic compounds such as B-Mg17Al12and AlMg phases. In addition, there were mass of Al4Mn phases distributed in eutectic layer.3. It is proposed and discussed that the forming mechanism of the ingot interface was due to the melt of1060plate instantaneous after pouring and the bilateral liquid diffusion of magnesium and aluminum atoms finished insufficiently in reason of the rapid solidification of the interfacial molten pool. The diffusion fusion layer near to as-cast Mg-2.0Mn-0.6Ca alloys is formed by partial "melting liquid" recrystallization process. While the diffusion fusion layer near to1060aluminum alloys is formed by Solid phase transform process due to atomic diffuse.4. The best parameters of Al/Mg bimetal composites ingot during hot rolling and annealing process are as follows, rolling temperature is360～400℃, pass reduction of10～20%, cumulate reduction>80%, intermediate annealing for1h, and annealing at240℃for1h is used after hot rolling for solid diffusion. The best composite quality and an optimum comprehensive performance of Al/Mg composite plates are obtained by such processing.5. The combine mechanism of Al/Mg composite plates can be summarized as follows:At first, the Mg-Al inter-metallic compounds such as Mg17Al12and AlMg layer were broken down and refined by rolling force during hot rolling process. Then, as the cumulate reduction increase, the size of Al/Mg composite was constant elongation in length and width directions. The refined and broken down inter-metallic compounds in the interface can be "rheology" under the shear stress force, which lead to a uniformly distribution in Al/Mg composite interlayer. At last, the Al/Mg interface was combined by rolling process. |
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