Micro permanent magnets can be printed on a 3D printer

It is reported that scientists from Ural Federal University and Ural Branch of the Russian Academy of Sciences are determining the best conditions for 3D printing permanent magnets based on hard magnetic compounds of rare earth metals. This will enable small-scale production of magnets, giving them any shape in the manufacturing process and creating complex magnet configurations. The magnet is suitable for micro motors and generators where pacemakers work. In addition, the technology minimizes production waste and shortens production cycle. The description and experimental results of this method were published in the journal Magnetism and Magnetic Materials.

Micro permanent magnets printed on a 3D printer. Source: UrFU/Oksana Meleshchuk

Manufacturing complex and small magnets is not a simple task, but they are required in various special applications, mainly in the medical field. 3D printing is one of the most promising methods for manufacturing parts with complex shapes using magnetic hard materials. Scientists have successfully determined the optimal parameters for 3D printing of permanent magnets using selective laser sintering.

This is an additive manufacturing method, in which the magnetic material in the form of powder is sintered layer by layer into a 3D product of a given shape based on the previously created 3D model. This technology makes it possible to change the internal characteristics of magnets at almost all stages of production. For example, change the chemical composition of the compound, the degree of spatial orientation and texture of the crystal, and affect the coercivity (anti demagnetization).

Sample image and printing strategy after SLM. The red line represents the locus of the laser beam spot; Black dotted line, movement of beam focus and laser off.

"It is an arduous task to produce small magnets. Now they can only be manufactured by cutting a large magnet into small pieces. Due to mechanical processing, about half of the used materials become garbage. At the same time, cutting introduces a lot of defects in the near surface layer, which greatly degrades the performance of the magnet. Adding technology can avoid this situation and create complex magnets. This configuration is necessary for pacemakers, because only Only under a microscope can the rotor of the motor be assembled from an independent magnet. " Researcher Dmitry Neznakhin explained.

To print magnets, scientists poured special steel powder into the printer. Source: UrFU/Oksana Meleshchuk

At present, scientists have successfully manufactured permanent magnets with a thickness of about one millimeter, whose performance is similar to that of industrial magnets. The base is a powder containing samarium, zirconium, iron and titanium. The compound has the characteristics suitable for permanent magnets, but traditional manufacturing methods deprive most of the properties of the compound. So scientists decided to see if new technologies could preserve these properties.

"When using traditional methods to prepare permanent magnets based on these compounds, the performance of the finished product is far from the theoretical prediction. We found that when sintering samples, adding fusible powders extracted from samarium, copper and cobalt alloys can retain the magnetic characteristics of the main magnetic powder. The melting temperature of this alloy is lower than the performance change of the main alloy, which is why the final material maintains its coercivity and density." Dmitry Neznakhin added.

Fig. 4 SEM image of SLM (Sm1 − xZrx) Fe11Ti magnet when x=0.2: (1) epoxy resin; (2) Low melting point additive; (3) (Sm1-xZrx) Fe11Ti rapidly quenched alloy, (4) interaction zone.

At present, scientists are establishing the basic formation rules of the microstructure and magnetic properties of hard magnetic materials, and determining which magnetic materials can be used to manufacture permanent magnets by laser sintering. This includes testing how sintering methods affect the properties of another known magnetic matrix, an alloy of neodymium, iron, and boron. The next stage of work will be to produce large permanent magnets suitable for practical applications.

Source:Phase composition and magnetic properties of (Sm,Zr)Fe11Ti magnets produced by selective laser melting, Journal of Magnetism and Magnetic Materials (2022). DOI: 10.1016/j.jmmm.2022.169937