Investigations regarding a novel combination treatment of electron beam alloying and diamond-like carbon coating for highly stressed Al alloys

铝合金是一种很有吸引力的轻质材料，但其较低的硬度限制了它们在摩擦学应力下用于部件的可用性。薄的硬质涂层，特别是类金刚石碳涂层(DLC)，表现出优异的摩擦磨损性能。但由于对软质材料缺乏支撑作用，只能在有限的范围内使用。这一缺陷可以通过电子束(EB)对铝衬底进行液态表面处理并由此增加硬度来消除。该项目的目的是研究Al-基材-EB表面层-DLC复合材料涂层中特定材料的因果关系和弹塑性变形和裂纹形成的顺序。这使得基于知识的高负荷材料复合材料设计成为可能。为了全面理解，应逐步建立工艺参数-显微组织-性能-应力行为之间关系的科学知识链。在第一阶段，将对铝基模型合金/DLC涂层之间的界面产生基本的材料和机械上的理解，作为软铝基上的层复合材料功能的基础。因此，重点是分析模型合金的微观结构和它们的相关性能，以获得所需的DLC涂层的支撑和结合功能。通过对Al、Al-Si和Al-Si-Ni(X)模型合金的逐步研究，可以更容易地提取微结构成分对氧化和选择性溅射过程的影响，从而对DLC涂层的附着力和承载能力产生影响。接触模型结合了对复合材料的各个组件的机械特性和残余应力状态的综合分析。第一步是生成层状复合材料的真实弹性载荷/接触模型，以计算完整的应力和应变状态。重点研究了铝基模型合金/类金刚石涂层界面和类金刚石涂层中的临界von Mise应力和裂纹临界应力参数。确定应力或应变参数是否最终是关键的，即它是否导致裂纹的萌生或扩展，是通过与在裂纹测试和通过纳米压痕进行弹入分析中实际观察到的裂纹现象进行比较来做出的。根据这些新的基本发现，向与应用相关的技术合金的过渡将在第二阶段进行，以便能够解释非均质、多相多材料合金的机理。

Al alloys are attractive lightweight materials, but their low hardness limits their usability for components under tribological stress. Thin hard coatings, especially diamond-like carbon coatings (DLC), show excellent friction and wear behavior. But due to the lack of supporting effect on soft materials they can only be used to a limited extent. This lack can be eliminated by electron beam (EB) liquid phase surface treatment of the Al substrate and the resulting increase in hardness. The aim of the project is to investigate the material-specific cause-and-effect relationships and the sequence of elastic-plastic deformations and crack formation in the material composite Al-substrate - EB surface layer - DLC coating. This enables a knowledge-based design of the material composite for high loads. For a comprehensive understanding, a scientifically based chain of knowledge of the relationships between process parameters - microstructure - properties - stress behaviour is to be established stepwise. In phase I, a fundamental material and mechanistic understanding of the interface between Al-based model alloy/DLC-coating as a basis for the functionality of a layer composite on soft Al-substrate will be generated. Thereby, the focus is on the analysis of the microstructure of the model alloys and their relevant properties for the desired support and adhesion function for the DLC coating. The stepwise investigation of Al, Al-Si and Al-Si-Ni(x) model alloys allows an easier extraction of the effects of the microstructural constituents on e.g. oxidation and selective sputtering processes, and thus, on the adhesion and load capacity of the DLC coating. The comprehensive analysis of the individual components of the material composite with regard to their mechanical characteristics and the residual stress state is incorporated into the contact modelling. The first step is to generate a realistic elastic load/contact model of the layered composite in order to calculate the complete stress and strain states. Attention is paid to the exceeding of critical von Mises stresses and to crack-critical stress parameters in the interface Al-based model-alloy/DLC-coating as well as within the DLC. The decision whether a stress or strain parameter is ultimately critical, i.e. whether it leads to the initiation or propagation of cracks, is made in comparison with the crack phenomena actually observed in the crack test and in the pop-in analysis by means of nanoindentation. Based on these new basic findings, the transition to application-relevant technical alloys is to be made in phase II in order to be able to interpret the mechanisms of the heterogeneous, multiphase multi-material alloy.