Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Challenges to Fabricate Functionally Graded Rare Earth Based Permanent Bonded Magnets Via Powder-Based Additive Manufacturing
Submission Author:
Rafael Gitti , SC , Brazil
Co-Authors:
Rafael Gitti, Melissa Röhrig Martins Silva, Stefan Riegg, Kilian Schäfer, Carlos Ahrens, Paulo Wendhausen
Presenter: Rafael Gitti
doi://10.26678/ABCM.COBEM2021.COB2021-1996
Abstract
Aiming to create functionally graded materials (FGMs), challenges regarding both intrinsic and microstructural properties are still to be overcome. Particularly, the latter ones are strongly controlled by the elected processing route. In that regard, Additive Manufacturing (AM) emerges as a promising route to produce not only a wide range of geometric features but most importantly to induce a variety of microstructural characteristics. This principle also enables the generation of structures with engineered heterogeneities alongside a particular axis, resulting in a gradual change of properties and functionality. In the case of magnetic materials, for example, it is possible to manipulate the magnetic field lines for a particular configuration or spatial distribution by only creating structures with particular geometries. We propose that a similar effect could be achieved by varying the volumetric fraction of magnetic particles within the as-printed magnetic samples. This idea is inspired by a previous work of our group, in which it was demonstrated that the magnetic properties of Nd-Fe-B bonded magnets obtained via Laser Powder Bed Fusion (LPBF) can be tuned by controlling the volumetric porosity of the as-printed components. By changing the energy deposited over the powder bed, via variations on laser scan speed (LS) values, it was possible to control the porosity level, which varied between 5% and 40% in volume. In this sense, the present work focuses on the obtention of Nd-Fe-B bonded magnets via LPBF, varying the magnetic particle fraction along a preferred direction, producing a variable magnetic field. A mixture composed of 45% vol. PA-12 and 55% vol. Nd-Fe-B isotropic powder (MQP-S-11-9 grade) was laser processed into magnetic samples via the Selective Laser Sintering (SLS) technique. The AM process was carried out by consolidating individual sections of 5 mm height varying the LS values aiming to induce a variation on magnetic particles fraction alongside a particular axis via porosity control. Geometrical density measurements revealed that both strategies adopted were capable to induce a certain level of porosity. Although SEM analysis showed a variable porosity level on each printed section, it was not possible to determine where the porosity is located within the as-printed magnets. Magnetic flux density measurements on both surface and cross-section of the as-printed magnetic samples presented that magnetic flux is homogeneous regardless of the building strategy adopted. Thermal effects related to the own LPBF process change the porosity through the volume, assisting the densification process instead of controlling heterogeneities in each designed section.
Keywords
Nd-Fe-B bonded magnets, Functionally graded materials, Laser powder bed fusion, Magnetic Properties
