Consolidation and characterization of additive manufactured multi-material components for electrical machines

Electrical machines are essential devices in several application domains such as electric vehicles and renewable energy systems owing to the conversion of electrical energy into mechanical energy as well as the turning of mechanical power to electricity. Nevertheless, the traditional production methods limit the design of electrical machines thus resulting in non-optimized power densities and energy efficiencies. Additive Manufacturing (AM) techniques offer a solution for the design of complex geometries and the combination of different materials since electrical machines require the employment of electric (Cu) and magnetic conductive materials (FeSi or FeCo) along with electrical insulators (glass ceramics). Fused Filament Fabrication and Robocasting are among the most suited processes as the shaping and densification of the powders occurs in separate manufacturing stages allowing the processing of brittle materials. In these extrusion based AM techniques the debinding and sintering steps represent a crucial point for the manufacturing of electrical machines: the achievement of highly dense components that are as free of contaminants as possible enables to obtain the best conductivity and magnetic properties. Therefore this PhD research work aims at optimizing the consolidation phase of the process by facing the main challenges of printing multi-material parts i.e. the differences in the thermal expansion coefficient and in the sintering temperature and the chemical compatibility of the FeSi/ceramic/Cu combinations. The fine-tuning of the processing will be carried out by investigating the microstructural characteristics, including the grain size and dislocation density, and their influence on the magnetic and electrical properties. Furthermore the mechanical rigidity of the multi-material components will be evaluated through measurements of the tensile bond strength and shear adhesion strength.