A rapid thermal-radiation-assisted sintering strategy for Nd-Fe-B-type magnets

The green transition has spiked demand for high-performance sintered Nd-Fe-B permanent magnets, necessitating advanced powder consolidation technologies to enhance production efficiency. This study explores the rapid sintering methodology for an Nd-Fe-B powder using a radiation-assisted sintering approach. The case study material is an industrially used powder, prepared through strip-casting, hydrogen decrepitation, and jet milling, with a mean particle size of 5.5 µm. The powder is sintered to full density in a modified spark plasma sintering furnace, achieving pressureless conditions and eliminating electrical currents in the sample to preserve grain alignment and prevent decomposition of the hard-magnetic phase. Fully dense samples are obtained with heating rates ranging from 10 to 200 °C min${}^{-1}$ and up to 5 min of dwell time at 1100 °C. Rapid heating results in grain size and microstructure comparable to conventionally sintered magnets prepared from the same powder, without compromising magnetic performance after postsinter annealing at 520 °C for 120 min. This sintering method contributes to a novel strategy for optimizing magnet production by utilizing efficient thermal-radiation heat transfer. The combination of rapid heating and pressureless sintering drastically reduces heat-up and dwell times, providing a fundamental advantage over slow conventional sintering. (© 2024 The Author(s). Advanced Engineering Materials published by Wiley‐VCH GmbH)