HYDROGEN DECREPITATED ANISOTROPIC ND-FE-B POWDER - HYDROGEN DESORPTION AND MAGNETIC-PROPERTIES

The hydrogen decrepitation (HD) process easily pulverizes rapidly soli dified, hot-deformed Nd-Fe-B (MQ3) magnets but degrades the magnetic p roperties. Recovery of high-performance magnetism in HD MQ3 powder has always required hydrogen desorption at temperatures above 600-degrees -C. It is reported that desorption at the relatively low temperature o f 240-degrees-C restores magnetic coercivity H(ci) to above 10 kOe des pite residual hydrogen in the material. Desorption between 240 and 580 -degrees-C significantly degrades H(ci) but not the intrinsic magnetic anisotropy. Hydrogen is reabsorbed when the desorbed powder is cooled from above 600-degrees-C to room temperature in the presence of small amounts of residual hydrogen gas. This hydrogen reabsorption strongly degrades the coercivity but does not affect the intrinsic magnetic an isotropy.