| Clad material, a new type of material of functional and structural material, has been widely used in the fields of aerospace, oil, chemical industry, automobile, military, metallurgy and machinery et al. It has become one of research focuses in material field since its excellent designability and combination property. As composite material, bonding interface is the most important microstructure for the clad material. It’s the passageway for the transmission of stress and other messages, and the structure and property of the bonding interface determine the performance of the clad material. Therefore, the intensive study on the forming process, quality, reaction and relevant influencing factors of bonding interface is the key for producing high-performance clad material.In this dissertation, two different types of cladding ingots were produced by compound casting. One is the3003/8090aluminum-aluminum cladding ingots which have not interface reaction between3003and8090, the other is the5056/AZ91aluminum-magnesium cladding ingots with interface reaction between Al alloy and Mg alloy. The solidification structure, element distribution, phase composition and mechanical property near the bonding interface were investigated by metallographic examination, EPMA, SEM, XRD and Vickers hardness tester et al. All of the experiments were carried out for providing experimental basis for continuous casting of these clad materials.The electromagnetic stirring (EMS) was used to improve solidification structure of8090alloy during the casting, and the effect of EMS on the interface morphology of this aluminum alloy cladding ingots was also studied. The results showed that with the influence of electromagnetic stirring, the solidification structure of8090alloy was obviously refined, the columnar-equiaxed transition (CET) was promoted, and solute-enriched in the grain boundary decreased. With the increase of magnetic field intensity, the columnar grains near the interface were deflected to the coming flow, until all of them transformed to equiaxed grains. However, the distribution of elements along the interface was nearly not much impact by EMS. In the condition with or without EMS, the average diffusion layers were all about90μm and the transition layer of sosoloid were about50μm. The transition layer resulted in the slow decrease of mechanical property in the interface zone, which ensured the good metallurgy bonding between two alloys. The bond strength met the requirement of the application.While for the5056/AZ91cladding ingots, with or without electromagnetic stirring, there were the reaction zone between5056and AZ91alloy. In the neighborhood of5056the intermetallic compound was Mg2Al3, and adjacent to the AZ91was Mg17Al12. The cladding ingot, with the thickness of the reaction zone was about2.3mm, was produced. The reaction zone was composed of four different types of solidification structure. From the AZ91side to the5056side, they were, in order,(Mg17Al12+δ-Mg) eutectic layer, Mg17Al12+(Mg17Al12+δ-Mg) transition layer, Mg17Al12phase layer and Mg2Al3phase layer. The brittleness intermetallic compound in the interface region resulted in the decrease of bonding strength between Al alloy and Mg alloy. The methods of EMS and changing pouring temperature of the inner or outer layer melt were not useful for avoiding or suppressing the formation of intermetallic compound in the interface. Therefore, for producing high-performance Al/Mg clad materials, the effective technology to control of the degree of the reaction between the aluminum and magnesium should be investigated in the future. |
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