  Bonded permanent magnets are key components in many energy conversion, sensor
and actuator devices. These applications require high magnetic performance and
freedom of shape. With additive manufacturing processes, for example laser
powder bed fusion (LPBF), it is possible to produce bonded magnets with
customized stray field distribution. Up to now, most studies use spherical
powders as magnetic fillers due to their good flowability. Here, the behavior
of large SmFeN platelets with a high aspect ratio as filler material and its
influence on the arrangement and the resulting magnetic properties are examined
in comparison to a spherical magnetic filler. The 3D distribution and
orientation of the magnetic filler was studied by computed tomography and
digital image analysis. The platelet-shaped particles align themselves
perpendicular to the buildup direction during the process, which offers a new
and cost-effective way of producing composites by LPBF with anisotropic
structural and functional properties. The influence of LPBF parameters on the
properties of the composites is investigated. Highest filling fractions are
required for high magnetic remanence, however the powder itself limits this
maximum due to particle shape and required minimal polymer fraction to form
mechanically stable magnets. The coercivity decreases for higher filling
fractions, which is attributed to increased rotation of insufficiently embedded
magnetic particles in the matrix. It is discussed how filler morphology
influences the observed change in coercivity since the rotation of spherical
particles in comparison to platelet-shaped particles requires less energy. Our
work shows the challenges and opportunities of large platelet shaped fillers
used in LPBF for the production of anisotropic functional and structural
composites.
