Correlation between Residual Stress, Building Angle and Illumination Parameters of Additive Manufactured FeSi6.5 and Mechanical and Magnetic Properties

Soft magnetic iron-silicon (FeSi) alloys are widely used in electromechanical energy converters. The addition of silicon to pure iron causes a reduction in electrical conductivity, which reduces the losses in energy conversion due to eddy currents. The main tasks of FeSi alloys are the low-loss guidance of the magnetic flux as well as the transfer of heat, torque and forces. Conventional processing is carried out by processing sheet material. The desired contour is cut out by punching, laser cutting or EDM, which is then stacked and joined to form a soft magnetic core. For high-alloy materials, punching in particular reaches its limits due to the brittle material behavior. Furthermore, punching processes are limited to axial symmetrical geometries. As a result, it is not economical to produce geometries adapted to an optimum magnetic flux path in the axial direction or to save material and thus weight in regions of low flux density. With Additive Manufacturing (AM), a workpiece is built up without tools, which enables a new dimension of the geometric design freedom. One method for AM of metals is laser beam melting (LBM). During the process, not only the geometry is materialized, but also the microstructure and hence the magnetic properties. Due to the working principle of LBM, residual stresses, which lead to deformation and to a reduction of the characteristic mechanical values, are inevitable. These downsides can be compensated by employing special pre-, in-and post-processing measures. The scope of this publication is to quantify the correlation between the part orientation inside the building chamber, residual stresses induced by different illumination patterns, and a post heat treatment process. The measurements are carried out under standardized conditions for better comparability with conventional materials.