Fabrication of High-Density Zn-Bonded Sm–Fe–N Bulk Magnets via High-Velocity Compaction

High-velocity compaction (HVC) using a die was investigated as a compaction technique for the fabrication of high-density isotropic Zn-bonded Sm–Fe–N bulk magnets. The compaction characteristics of Zn-mixed Sm–Fe–N powders obtained by HVC were investigated while varying the Zn content. Moreover, the magnetic properties, flexural strengths (σ), and microstructures of the resulting magnets were studied. The relative density (dr) steadily increased with the piston velocity during compaction and reached approximately 90% at a piston velocity of 11.2 m·s−1 (equivalent to a compaction pressure of 3.45 GPa), regardless of the Zn content. Because the magnets were fabricated using a die, they also had a high dimensional precision. The resulting magnet, with 5 wt% Zn and dr of 89.1%, exhibited a maximum energy product ((BH)Max) of 54.4 kJ·m−3, remanence (Br) of 0.56 T, and coercivity (HcJ) of 965 kA·m−1. σ exceeded 100 MPa when dr was above 88%, which satisfies the required mechanical strength for applications such as permanent magnet motors.