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Influence of Powder Loading Fraction on Properties of Bonded Permanent Magnets Prepared By Selective Laser Sintering
Martin Mapley1,2, Shaun D Gregory3, Jo P Pauls1,2
1School of Engineering and Built Environment, Griffith University, Queensland, Australia.
3D Printing and Additive Manufacturing
|January 19, 2023
Summary
Researchers explored using selective laser sintering (SLS) to create bonded permanent magnets (PMs) with higher magnetic powder content. They found flake powders offer superior mechanical properties and magnetic performance compared to spherical powders, highlighting an application-specific trade-off.
Area of Science:
- Materials Science
- Additive Manufacturing
- Magnetism
Background:
- Selective Laser Sintering (SLS) is used to produce bonded permanent magnets (PMs) from neodymium-iron-boron (Nd-Fe-B) and polyamide-12 powders.
- Increasing magnetic powder loading fraction in SLS-produced PMs aims to enhance magnetic performance.
- Reduced binder content, necessary for higher magnetic loading, can compromise mechanical strength due to incomplete particle infiltration.
Purpose of the Study:
- To investigate the mechanical properties and residual induction of PMs produced via SLS with varying loading fractions (10-90%) of spherical and flake Nd-Fe-B powders.
- To determine the maximum attainable loading fractions for both powder morphologies.
- To analyze the relationship between powder loading fraction and magnetic/mechanical properties.
Main Methods:
- Selective Laser Sintering (SLS) was employed to process mixtures of Nd-Fe-B (spherical and flake) and polyamide-12 powders.
- Mechanical properties (elastic modulus, strain limit) and residual induction were measured across a range of magnetic powder loading fractions.
- Density was also assessed to understand material consolidation.
Main Results:
- Maximum attainable loading fractions were 80%/vol for flake and 70%/vol for spherical Nd-Fe-B powders.
- PMs from flake powders achieved peak density and residual induction at 50%/vol loading, while spherical powders peaked at 70%/vol.
- Spherical powders showed diminishing returns in density and induction beyond 30%/vol, whereas flake powders exhibited superior mechanical properties despite a general decrease in strength with increased loading.
Conclusions:
- Bonded PMs produced from flake Nd-Fe-B powders via SLS demonstrate better mechanical properties and magnetic performance compared to those made from spherical powders.
- Optimal magnetic performance is achieved at 50%/vol loading for flake powders and 70%/vol for spherical powders, with spherical powders showing a significant plateau effect.
- The study underscores the necessity of balancing mechanical integrity and magnetic strength based on specific application requirements when utilizing SLS for PM fabrication.
