Microstructure and magnetic properties of PrFeCoBnB sintered magnets produced from HD and HDDR powders

Abstract

Sintered magnets have been produced with powder obtained using the hydrogenation, disproportionation, desorption and recombination process (HDDR). The new processing procedure for the production of the sintered magnets has been adopted in an attempt to reduce the milling time. Commercial cast ingot alloys based on the compositions Pr14Fe75.9Co4B6Nb0.1 and Pr20.5FebalB5Cu2.0 have been employed in this investigation. The HDDR powder was used to produce sintered magnets using a mixture of these alloys, in very distinct proportions. Only a small amount (20 wt. %) of the copper-containing alloy has been added as a sintering aid. Standard hydrogen decrepitation (HD) magnets have also been included in this work for a comparison. The effect of a reduced milling time on the magnetic properties of the HDDR sintered magnets has been investigated. Sintering temperature and time of were kept constant for all magnets (1050ºC for 60 minutes). The microstructures of the permanent magnets have been investigated by scanning electron microscopy and energy dispersive X-ray analysis.