【作者】 钟德水；

【导师】 李廷举；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2012， 硕士

【摘要】 金属复层材料作为一种新型的功能、结构材料,由于其优良的可设计性及综合性能,被广泛应用于宇航、石油、化工、汽车、军事、冶金、机械等领域,是近年来材料科学的研究热点之一。作为复合材料,结合界面是金属复层材料最为重要的微结构,是应力及其他信息相互传递的桥梁,其结构与性能直接影响复合材料的整体性能。因此,深入研究结合界面的形成过程、界面层性质、界面反应及其影响因素,从而进行有效控制,是获取高性能金属复层材料的关键。本文采用静态复合铸造工艺,分别制备了两类具有不同结合方式的金属复层铸锭,一类是没有界面反应的8090/3003铝-铝复层铸锭,一类是有界面反应的5056/AZ91铝-镁复层铸锭。采用金相、电子探针、扫面电镜、X射线衍射及维氏硬度计等测试手段对两种复层铸锭的界面凝固组织、成分分布、物相组成及力学性能等进行了系统分析。一系列静态试验研究是为实现两类复层铸坯的连铸铸造打下良好基础。对3003/8090复层铸锭的内层8090合金施加电磁搅拌,研究了电磁搅拌对复层铸锭界面形貌的影响,实验结果表明：电磁搅拌使内层8090合金凝固组织明显细化,促进柱状晶向等轴晶转变。随着电磁搅拌的增强,结合界面前沿处的柱状晶的生长向逆流方向偏转,直至完全转化为细小等轴晶；但是电磁搅拌对结合处界面的成分分布无显著影响,有无电磁搅拌的情况下,扩散层厚度均约为90μm,其中过渡固溶体层约为50μmm。过渡层的存在,使得力学性能在结合界面内平缓过渡,保证了两侧合金良好的冶金结合,结合强度满足实际应用要求。对于5056/AZ91复层铸锭,在有无电磁搅拌的情况下,5056与AZ91间均发生剧烈界面反应而形成反应层。在5056一侧多为Mg2Al3,而在AZ91一侧多为Mg17Al12。实验获得反应层约为2.3mm的5056/AZ91复层铸锭,其反应层由4层不同的凝固组织构成,由AZ91侧至5056侧依次为(Mg17Al12+α-Mg)共晶层、Mg17Al12+(Mg17Al12+α-Mg)过渡层、Mg17A112单相层及Mg2Al3单相层。反应层内的金属间化合物具有极强的脆性,从而导致铝／镁复层铸锭的界面结合强度极低。通过电磁搅拌作用、降低AZ91浇注温度及5056凝固壳内表面温度等手段仍无法抑制或避免界面处金属间化合物的形成。因此,为了获得具有良好结合的铝／镁复层材料,有待展开进一步的研究,采用有效的工艺技术控制铝、镁间的反应程度。更多还原

【Abstract】 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.更多还原