Influence of heat treatment on microstructure and magnetic properties of laser powder bed fusion generated NdFeB magnets

Laser powder bed fusion (L-PBF) presents a promising technique for producing neodymium–iron–boron (NdFeB) magnets. However, the magnetic properties of L-PBF-generated magnets remain inferior to those of their sintered counterparts. To address this, post-processing techniques, such as heat treatment, could enhance the magnetic properties of L-PBF-fabricated NdFeB magnets. This study examines the effects of post-heat treatment on the density, magnetic properties, and microstructure of samples produced using MQP-S-11-9-20001 powder. Archimedes density measurements indicate an improvement of up to 5% in density following heat treatment, corroborated by optical images showing decreased porosity. Analysis of magnetic properties reveals an increase in remanence (Br) alongside a decrease in coercivity (Hci). Microstructural analysis indicates variations in grain size and morphology, with more distinct grain boundaries contributing to enhanced coercivity. The study also highlights challenges in analyzing high-temperature treated samples, particularly due to their extreme sensitivity to oxygen and etching difficulties. Despite these challenges, the findings offer valuable insights into how heat treatment affects the microstructure of L-PBF-generated NdFeB magnets and the resultant changes in their magnetic properties.