Hot pressing Nd-Fe-B HDDR powders

Abstract

Details of the important parameters for hot pressing isotropic Nd16Fe76BS HDDR powders are presented. Optimum magnetic properties may he achieved over broad ranges of green compaction pressure .and hot pressing temperature, time and pressure. Isotropic HDDR powders with lower Ndcontents (i.e. Nd14Fe79B7 and N d 1 3 F e 8 0 . 5 B 6 . 5 ) may also be hot pressed to full density to p5oduce magnets with energy products -1 0 0 k J / m and some advantages of hot pressing the lower Ndcontent compositions are stated. The cause of t h e enhanced values of remanence obtained for nominally isotropic hot pressed HDDR magnets i s probably due to some alignment induced during h o t pressing.The ease of hot pressing HDDR powder suggests this process is commercially v i a h l e , particularly as the HDDR powder production p r o c e s s has been estimated to he cheaper than that of t h e MQ powder.

Coercivity enhancement of HDDR-processed Nd–Fe–B permanent magnet with the rapid hot-press consolidation process

“…Such a phenomenon has not been reported in previous studies using the conventional hot-press [8,[14][15][16] or the SPS apparatus [10,11]. Moreover, a high H cJ surpassing that of the initial HDDR powder by 25% has been obtained with this process.…”

Permanent magnets based on R-Fe-B and R-Fe-C alloys

“…Estevez et al (1994) found, for the same composition, some submicron grains with no Nd-rich phase and some isolated by the Nd-rich phase. Ragg et al (1996) analysed the influence of green compacting pressure and hot pressing temperature, time and pressure on the properties of Nd-Fe-B HDDR powder. Magnets with energy products close to 100 kJ m −3 have been achieved for a hot-pressed Nd 14 Fe 79 B 7 magnet.…”

Fundamental and practical aspects of the hydrogenation, disproportionation, desorption and recombination process

“…Further work in Birmingham [49] has focused on the effects of the hot-pressing parameters on the resultant magnetic properties of the hot-pressed fully dense Nd 16 Fe 76 B 8 HDDR magnets. The possibility of reducing the Nd content (and thereby raising the iron content), in order to increase magnetic properties was also investigated.…”