Processing of thin metal sheets of air‐hardening steels differs from the usual processing and includes deep drawing in the ferritic condition, a cutting operation and a thermal treatment of austenitizing, air quenching and an optional tempering, respectively. The mechanical properties of the low carbon steel LH800 increase due to air‐hardening, e.g., the tensile strength rises from about 480 MPa in the as‐delivered ferritic condition up to more than 1000 MPa in the martensitic condition. The experimental work aims to create a dual phase microstructure consisting of martensite and ferrite by austenitizing below the Ac3 temperature and to characterize the mechanical properties. Based on the experimental data mechanical properties and microstructural parameters could be correlated. For example, the tensile strength can be calculated using the rule of mixture for the microstructure fractions of martensite and ferrite. The yield stress can be predicted by extending the rule of mixture regarding the Hall–Petch equation. As the results reveal the mechanical properties can be controlled very well regarding tensile strength and yield stress by austenitizing at comparatively low temperatures.

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A new approach for the development of thermoelectric materials, which focuses on a high-power factor instead of a large figure of merit zT, has drawn attention in recent years. In this context, the thermoelectric properties of Cu-Ni-based alloys with a very high electrical conductivity, a moderate Seebeck coefficient, and therefore a high power factor are presented as promising low-cost alternative materials for applications aiming to have a high electrical power output. The Cu-Ni-based alloys are prepared via an arc melting process of metallic nanopowders. The heavy elements tin and tungsten are chosen for alloying to further improve the power factor while simultaneously reducing the high thermal conductivity of the resulting metal alloy, which also has a positive effect on the zT value. Overall, the samples prepared with low amounts of Sn and W show an increase in the power factor and figure of merit zT compared to the pure Cu-Ni alloy. These results demonstrate the potential of these often overlooked metal alloys and the utilization of nanopowders for thermoelectric energy conversion.

Within the framework of the Collaborative Research Center 1153, we investigated novel process chains for the production of bulk components with different metals as joining partners. In the present study, the co-extrusion of coaxially reinforced hollow profiles was employed to manufacture semi-finished products for a subsequent die-forging process, which was then used for the manufacture of hybrid bearing bushings. The hybrid hollow profiles, made of the aluminum alloy EN AW-6082 paired with either the case-hardening steel 20MnCr5, the stainless steel X5CrNi18-10, or the rolling bearing steel 100Cr6, were produced by Lateral Angular Co-Extrusion. Push-out tests on hybrid hollow sections over the entire sample cross-section showed shear strengths of 44 MPa ± 8 MPa (100Cr6) up to 63 MPa ± 5 MPa (X5CrNi18-10). In particular, the influence of force and form closure on the joint zone could be determined using specimen segments tested in shear compression. Locally, shear strengths of up to 131 MPa (X5CrNi18-10) were demonstrated in the shear compression test. From these samples, lamellae for microstructural analysis were prepared with a Focused Ion Beam. Detailed analyses showed that for all material combinations, a material bond in the form of an ultra-thin intermetallic phase seam with a thickness of up to 50 nm could be established.

The development of a novel manufacturing process chain is a complex scientific challenge and requires interdisciplinary and inter-institutional collaboration. Data need to be exchanged continuously between involved researchers in order to coordinate between individual process steps and to identify cause-effect relationships within the process. This publication describes an approach to provide seamless digital access to quality-related data and to further structure, semantically annotate and link process-and quality-relevant data. It uses a domain-specific ontology called Visual Inspection Ontology embedded in a Knowledge Management System to support the documentation of a qualitydetermining process. The ontology is applied to a use case from the development of a novel process chain to manufacture multi-material shafts within the Collaborative Research Centre (CRC) 1153. A workflow to establish quality control measures regarding a novel process chain for multi-material highperformance components under development based on the proposed ontology is presented.