Influence of preparation processes with or without long-time homogenization heat treatment on performance of Nd–Fe–B HDDR products

Abstract

We investigated the influence of hydrogenation-disproportionation-desorption-recombination (HDDR) preparation processes, with or without long-time homogenization heat treatment, on the microstructure and hard magnetic properties of Nd12.7B6.5Co2.1Cr0.1Al0.5Nb0.3Ga0.5Fe77.3 powders/bonded magnets. Hard magnetic properties such as remanence (Br = 1.01 T), coercivity (Hcj = 949.39 kA/m), and maximum magnetic energy product (BH)max = 181.54 kJ/m3 were achieved for HDDR bonded magnets with homogenization heat treatment. In contrast, magnets prepared without homogenization heat treatment exhibited Br = 0.65 T, Hcj = 854.69 kA/m, and (BH)max = 66.98 kJ/m3. The notable decrease in remanence for magnets prepared without homogenization treatment is attributed to the presence of α–Fe in the parent alloy, which inhibits the hydrogenation-disproportionation process and consequently affects the orientation of the crystallographic texture. Furthermore, we fabricated bonded quadrupole magnetic rings using HDDR powder prepared with homogenization heat treatment. The study also explored the relationship between disproportionation temperature and surface magnetic field intensity for these quadrupole magnetic rings.