Resource-efficient manufacturing with a high degree of freedom in terms of component shape can be realised through additive manufacturing. The focus can lie not only on the manufacturing process in terms of geometrical correctness, stability, etc., but also on the targeted development of specific material properties. This study shows the development of hybrid material systems made of aluminium and the ferromagnetic particles iron, cobalt, and nickel. The aim is to use the ferromagnetic properties as sensor properties to enable the easy sensing of material properties such as the microstructure, fatigue, or occurring stresses. To easily adopt different compositions, hot isostatic pressing was selected for the characterisation of the material composites Al-Fe, Al-Ni, and Al-Co with regard to their magnetic properties. Subsequently, transfer to the additive manufacturing process of wire and arc additive manufacturing gas metal arc welding was carried out by mixing the powder separately into the weld pool. The study shows that it is possible to prevent a complete transformation of Ni and Co into intermetallic phases with Al by adjusting the influencing variables in the HIP process. Magnetic properties could be detected in the composites of Al-Co and Al-Fe. This work serves as a preliminary work to realise additive components made of hybrid material systems of Al-Fe, Al-Co, and Al-Ni with the GMA welding process.

In the area of plant engineering, steel components are provided with a wear protection coating for efficient use to protect them against corrosive, tribological, thermal and mechanical stresses. The use of innovative ultrasound-assisted milling processes and plasma-welded nickel- and cobalt-based wear protection coatings are being investigated to determine how more favourable machinability can be achieved while retaining the same wear protection potential. The focus is on the NiCrSiFeB alloy, which is intended to replace CoCr alloys in the area of screw machines. The utilization of ultrasonic-assisted milling for the machining of coating materials is a novel approach. The modification of hard facing layers in terms of microstructure and precipitation morphology as well as suitability for machining is investigated and compared with the CoCr alloy. The alloy modifications are generated by a PTA process by systematically adjusting the preheating and interpass temperatures, a crack-free wear-resistant layer can be generated, which is subsequently machined by a milling process. In addition to the crack-free properties, the microstructure, the bonding as well as the mixing between the NiCrSiFeB alloy and a 1.8550 as well as between the CoCr alloy and a 1.4828 are analysed and compared in the joining areas. In addition, heating and cooling rates are determined and a chemical analysis of the weld metals is performed. Furthermore, it was found that the build-up layers of NiCrSiFeB alloy are more difficult to machine using the milling process than the CoCr alloy, as higher milling forces are required.

Ferromagnetic alloys exhibit the Villari effect, whereby applied stress changes their magnetization and permeability, making them intrinsically load-sensitive. These stress-dependent magnetic properties enable sensing via magnetic excitation and readout. Compared with strain gauges, ferromagnetic alloys can offer high sensitivity, a broad load range, robustness in harsh environments, low cost and low-maintenance structural health monitoring. In the present study, a hybrid material system consisting of an Al base material and ferromagnetic particles of Co, Ni, and pre-oxidized Fe is realized by high isostatic pressing. The magnetic properties are then characterized using harmonic analysis of the eddy current signals, both under no load and under load during tensile tests. Analysis of the third harmonic showed that the Al composite with pre-oxidized iron exhibited the most pronounced magnetic properties. Generally, the composites exhibit different signal amplitudes under tensile stress, depending on the added ferromagnetic material. The amplitude of the third harmonic of aluminum with pre-oxidized iron vs. elongation shows a clear inflection point. This demonstrates the potential of this composite material for use as a sensor material. Adding ferromagnetic particles to aluminum increases the yield strength. Analysis of the fracture surfaces shows that the fracture behavior is related to the intermetallic phases formed with Al. When using pre-oxidized iron, the detachment of particles from the matrix is the dominant mechanism of damage.