CONSOLIDATION OF MAGNETIC POWDERS BY SHOCK COMPRESSION

The application of shock consolidation of powder precursors using expl osives for the processing of bulk permanent magnet materials was studi ed. Powders of Sm-Fe-N and Nd-Fe-B produced by milling of ingot materi al, mechanical alloying, hydrogenation-disproportionation-desorption a nd recombination (HDDR), or by pulverizing of melt-spun ribbon were pr essed at a shock wave speed of 1200 m s(-1) and pressures up to 4.4 GP a. It was found that consolidation of the hard magnetic powders could be achieved without changes of the phase structure and grain size and that the resulting bulk magnets had high coercivities and remanences. The final density depended on the composition of the material and on t he initial grain size. The shock processing method was found to be par ticularly appropriate for the consolidation of nanostructured material s for which excessive grain growth during consolidation must be avoide d. (C) 1998 Chapman & Hall.