Influence of colloidal additivation with surfactant-free laser-generated metal nanoparticles on the microstructure of suction-cast Nd-Fe-B alloy

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 ZrB${}_2$, 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. ZrB${}_2$ 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. (© 2023 The Authors. Advanced Engineering Materials published by Wiley‐VCH GmbH)