EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Innovative material concepts are crucial for modern technological applications, e.g. the thermal management of power electronics or high-current power switches. Therefore, a composite material uniting the temperature resistance and hardness of W as well as the ductility and conductivity of Cu is used. Hence, new approaches to simultaneously improve the inherently diverging fracture toughness and strength have to be applied. Thus, within this work, a W-Cu nanocomposite was produced using the high pressure torsion method and the micro-mechanical properties were illuminated. Furthermore, different deformation ratios were applied to obtain varying grain sizes, affecting conditional fracture toughness, J-integral and hardness of the material. The microstructure of the deformed specimens was analyzed by scanning electron microscopy, transmission electron microscopy and selected area diffraction. Also, the grain size distribution of the W grains within the composite was analyzed by a customized watershed segmentation tool. Employing nanoindentation, the hardness and Young’s modulus were determined for the different deformation ratios. This enabled to optimize the grain size towards balanced mechanical properties. The conditional fracture toughness and J-integral are determined by in-situ micro cantilever experiments, yielding the dynamic compliance. This allows to determine the actual length of the propagating crack within the cantilever. Simultaneously, the crack propagation is tracked on the surface of the specimen by scanning electron microscopy. The application of different methods allows to determine the most favorable degree of deformation and their corresponding mechanical properties.