Abstract The casting of liquid melt on a preheated substrate layer to produce a metallurgical compound represents a direct approach towards clad aluminum strips. To investigate this direct process route and the formation of a metallurgical bond at the interface, a small-scale pilot plant to cast pure aluminum on strips of aluminum alloy 7075 under controlled conditions was developed. Composite casting plates were produced at varying casting parameters (preheating temperature of the substrate, clad layer thickness, casting speed, melt temperature) and subsequently analyzed by metallographic means to classify the bond quality. Suitable thermal conditions for the melt flow in the casting device were found by numerical simulation using a commercial fluid flow and solidification software package. Additional meso- and micro-modeling of the casting and the bonding zone supported the understanding of the bonding mechanism. The heat transfer in the macro-model of the casting device was calibrated using measured temperatures obtained during compound casting experiments. A finer meshed two-dimensional meso-model of the casting device was derived from the macro-model to gain more accurate information about the temperature distribution in the vicinity of the bonding zone. This interface between the pure aluminum and the aluminum alloy was modeled in extremely high temporal and spatial resolution (micro-model) as temperatures are not accessible there by direct measurements. These simulation results show the time-resolved re-melting and re-solidification of the aluminum alloy during compound formation. The obtained simulation results correlate very well with electrochemically etched cross sections of cast bilayer aluminum strips. The experiments show that the oxide layer at the interface has to be removed completely during the casting process to obtain high quality compounds. The assumed mechanism of detachment and transport of the fractured oxide is shown schematically and necessary thermo-mechanical conditions for the removal of the oxide skin are discussed.

中文翻译：

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铝复合铸造工艺的开发——实验和数值模拟

摘要 在预热的基材层上浇铸液态熔体以生产冶金化合物代表了一种直接的包覆铝带方法。为了研究这种直接工艺路线和界面处冶金结合的形成，开发了一个在受控条件下在 7075 铝合金带上铸造纯铝的小规模试验工厂。在不同的铸造参数（基材的预热温度、复合层厚度​​、铸造速度、熔体温度）下生产复合铸造板，然后通过金相方法分析以对结合质量进行分类。通过使用商业流体流动和凝固软件包的数值模拟，找到适合铸造装置中熔体流动的热条件。铸件和结合区的额外细观和微观建模支持了对结合机制的理解。铸造装置的宏观模型中的热传递使用复合铸造实验中获得的测量温度进行校准。从宏观模型中推导出更精细网格的铸造设备二维细观模型，以获得有关结合区附近温度分布的更准确信息。由于无法通过直接测量获得温度，因此纯铝和铝合金之间的界面以极高的时间和空间分辨率（微观模型）建模。这些模拟结果显示了铝合金在复合形成过程中的时间分辨再熔化和再凝固。获得的模拟结果与铸造双层铝带的电化学蚀刻横截面非常相关。实验表明，在铸造过程中必须完全去除界面处的氧化层才能获得高质量的化合物。示意性地显示了断裂氧化物的分离和传输的假设机制，并讨论了去除氧化皮所需的热机械条件。