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Development of new powder feedstocks using nanoparticles (NPs) has the potential to influence the microstructure of as-built parts and overcome the limitations of current powder-based additive manufacturing (AM) techniques. The focus of this study is to investigate the impact of NP-modified magnetic microparticle powder feedstock on the microstructure of suction-cast Nd-Fe-B-based alloys. This particular casting method has been recognized for its ability to replicate, to some extent, the melting and rapid solidification stages inherent to metal powder-based AM techniques such as powder bed fusion using a laser beam. Two types of NP materials, Ag and ZrB2, are used, and their effects on the grain size distribution and dendritic structures are evaluated after suction casting. Ag NPs result in smaller, more uniform grain sizes. ZrB2 NPs result in uniformly distributed grain sizes at much lower mass loadings. The results show that feedstock powder surface modification with low-melting-point metal NPs can improve permanent magnets' microstructure and magnetic properties, at below 1 vol%, equal to submonolayer surface loads. Herein, the potential of using NPs to develop new powder feedstocks for AM is highlighted, significantly improving the final part's properties. [ABSTRACT FROM AUTHOR]

In our search for an optimum soft magnet with excellent mechanical properties which can be used in applications centered around "electro mobility", nanocrystalline CoCrFeNiGax (x = 0.5, 1.0) bulk high entropy alloys (HEA) were successfully produced by spark plasma sintering (SPS) at 1073 K of HEA powders produced by high energy ball milling (HEBM). SPS of non-equiatomic CoCrFeNiGa0.5 particles results in the formation of a single-phase fcc bulk HEA, while for the equiatomic CoCrFeNiGa composition a mixture of bcc and fcc phases was found. For both compositions SEM/EDX analysis showed a predominant uniform distribution of the elements with only a small number of Cr-rich precipitates. High pressure torsion (HPT) of the bulk samples led to an increased homogeneity and a grain refinement: i.e., the crystallite size of the single fcc phase of CoCrFeNiGa0.5 decreased by a factor of 3; the crystallite size of the bcc and fcc phases of CoCrFeNiGa—by a factor of 4 and 10, respectively. The lattice strains substantially increased by nearly the same extent. After HPT the saturation magnetization (Ms) of the fcc phase of CoCrFeNiGa0.5 and its Curie temperature increased by 17% (up to 35 Am2/kg) and 31.5% (from 95 K to 125 K), respectively, whereas the coercivity decreased by a factor of 6. The overall Ms of the equiatomic CoCrFeNiGa decreased by 34% and 55% at 10 K and 300 K, respectively. At the same time the coercivity of CoCrFeNiGa increased by 50%. The HPT treatment of SPS-consolidated HEAs increased the Vickers hardness (Hv) by a factor of two (up to 5.632 ± 0.188) only for the non-equiatomic CoCrFeNiGa0.5, while for the equiatomic composition, the Hv remained unchanged (6.343–6.425 GPa). [ABSTRACT FROM AUTHOR]

The demand for strong, compact permanent magnets essential for the energy transition drives innovation in magnet manufacturing. Additive manufacturing, particularly Powder Bed Fusion of metals using a laser beam (PBF-LB/M), offers potential for near-net-shaped Nd-Fe-B permanent magnets but often falls short compared to conventional methods. A less explored strategy to enhance these magnets is feedstock modification with nanoparticles. It is demonstrated that modifying a Nd-Fe-B-based feedstock with 1 wt.% Ag nanoparticles boost the coercivity of the magnets to a record value of 935 ± 6 kA m -1 without further post-processing or heat treatments. Suitable volumetric energy densities for the PBF-LB/M process are determined using finite element simulations predicting melt pool behavior and part density. Microstructural analyses reveal finer grain sizes and more equiaxed nanocrystalline structures due to the modification. Atom probe tomography identifies three phases in the Ag-modified samples, with Ag forming nanophase regions with rare-earth elements near the amorphous Zr-Ti-B-rich intergranular phase, potentially decoupling the Nd 2 Fe 14 B primary phase. The study shows that superior magnetic properties primarily result from microstructure modification rather than part density. These findings highlight inventive material design approaches via feedstock surface modification to achieve superior magnetic performance in additively manufactured Nd-Fe-B magnets., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)