Production of bonded permanent magnets (PMs) by processing a mixture of neodymium-iron-boron (Nd-Fe-B) (spherical and flake) and polyamide-12 powders using selective laser sintering (SLS) has focused on increasing the magnetic powder loading fraction to improve the magnetic performance of PMs. However, when using SLS to produce PMs from mixed feedstock, the likelihood of the areas between the magnetic particles being infiltrated by the liquefied binder inducing particle bonding is reduced as binder content is reduced. This decreases mechanical strength and introduces upper limits to the attainable loading fraction of the magnetic powder. The present study investigated the mechanical properties and provided an insight into the residual induction, of loading fractions between 10% and 90% of spherical and flake powders when producing PMs using SLS. The maximum attainable loading fractions were 80%/vol and 70%/vol for the flake and spherical powders, respectively. The PMs produced from the flakes reached a maximum density and residual induction at 50%/vol loading fraction. The PMs produced from spherical powder reached maximum density and residual induction at 70%/vol loading fraction; however, a knee point at 30%/vol loading fraction demonstrated only minor improvements to density (8.8%) and residual induction (13.4%) with further increases in loading fraction. Although PMs produced from flakes demonstrated superior mechanical properties, the elastic modulus and strain limit rapidly decreased with increases in powder loading fraction for both powder types. This study demonstrated the application-specific balance between mechanical and magnetic strength that must be considered when producing PMs by using SLS.

中文翻译：

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载粉率对激光选区烧结粘结永磁体性能的影响

通过使用选择性激光烧结 (SLS) 处理钕铁硼 (Nd-Fe-B)（球形和片状）和聚酰胺 12 粉末的混合物来生产粘结永磁体 (PM) 的重点是增加磁粉负载提高 PM 磁性能的分数。然而，当使用 SLS 从混合原料生产 PM 时，随着粘合剂含量的减少，磁性颗粒之间的区域被液化粘合剂渗透导致颗粒结合的可能性降低。这会降低机械强度并为可达到的磁粉负载率引入上限。本研究调查了机械性能，并深入了解了残余感应，即使用 SLS 生产 PM 时负载分数在 10% 到 90% 之间的球形和片状粉末。片状和球形粉末的最大可达到负载分数分别为 80%/vol 和 70%/vol。由薄片产生的 PM 在 50%/vol 加载分数时达到最大密度和残余感应。由球形粉末制备的 PM 在 70%/vol 加载分数时达到最大密度和残余感应；然而，30%/vol 加载分数的拐点表明，随着加载分数的进一步增加，密度 (8.8%) 和残余诱导 (13.4%) 仅略有改善。尽管由薄片生产的 PM 表现出优异的机械性能，但弹性模量和应变极限随着两种粉末类型的粉末加载分数的增加而迅速下降。