Koichiro Morimoto

Influences of original alloy microstructure on magnetic properties of isotropic HDDR-treated Nd–Fe–B powder

Abstract Influences of original alloy microstructure on magnetic properties of the isotropic hydrogenation-decomposition-desorption-recombination-treated Nd 12.6 Fe 79.0 Co 2.4 B 6.0 powder were studied using two types of starting materials, i.e., the strip cast (SC) alloy and the conventional book-mold cast (BMC) alloy. It was found that the powder prepared from the SC alloy exhibits better I – H loop squareness and higher remanence than the powder from the BMC alloy. The powder obtained from the SC alloy consists of the recombined Nd 2 Fe 14 B grains with more uniform size, which is thought to be closely related to its good loop squareness. The effect of using the SC alloy could be attributed to the complete elimination of α-Fe phase.

Microstructure control in HDDR process for higher anisotropic Nd-Fe-B magnet powders

Homogenized Nd-Fe-Co-B-Zr(-Ga) alloys are treated by hydrogenation (HD-process) and dehydrogenation (DR-process) with various treatment conditions, followed by quenching in argon gas flow. After the HDDR process, the specimens are crashed into powders. The magnetic properties of the powder and bonded magnets are measured with a vibrating sample magnetometer and a B-H tracer. The microstructural changes are also analyzed by electron microscopy (FE-SEM and TEM) and discussed with special reference to the behavior of boron.