processed by the hydrogenation, disproportionation, desorption and recombination (HDDR) process

The hydrogenation, disproportionation, desorption and recombination (HDDR) process has been employed to produce -based permanent magnets. The master alloys for HDDR are -based alloys which are obtained by annealing mechanically alloyed (MA) powder at . The disproportionation reaction at results in the formation of an intimate mixture of Nd-hydride, and . On desorbing the hydrogen at the same temperature, different constituents recombine to form the thermodynamically stable and the Nd-rich phase, depending sensitively on recombination time and slightly on hydrogenation time. The phases obtained by HDDR at consist of , the Nd-rich phase and , whereas those obtained at are of , the Nd-rich phase and a small amount of . For comparison, the -based alloys have also been processed by HDDR, in which more and Nd-rich phases are found to coexist with after recombination at the same temperature. The -based alloy made by MA in conjunction with HDDR has better magnetic properties than that made by MA only.

[1]  X. Zhao,et al.  Nd - Fe - (C, B) permanent magnets made by mechanical alloying and subsequent annealing , 1996 .

[2]  Hajime Nakamura,et al.  Effects of additives on hydrogenation, disproportionation, desorption and recombination phenomena in Nd2Fe14B compounds , 1995 .

[3]  I. R. Harris,et al.  Kinetic studies on solid‐HDDR processes in Nd‐Fe‐B‐type alloys , 1994 .

[4]  Yingchang Yang,et al.  The effects of hydrogen disproportionation, desorption, and recombination on the structure and magnetic properties of Sm2Fe17Nx and NdFe10Mo2Nx compounds , 1994 .

[5]  N. Kuwano,et al.  Microstructures and crystallographic orientation of crystalline grains in anisotropic Nd‐Fe‐Co‐B‐(Ga or Zr) magnet powders produced by the hydrogenation‐decomposition‐desorption‐recombination process , 1994 .

[6]  B. Shen,et al.  A novel hard magnetic material for sintering permanent magnets , 1994 .

[7]  I. R. Harris,et al.  Development of microstructure of the disproportionated material during HDDR processes in a Nd16Fe76B8 alloy , 1994 .

[8]  C. Christodoulou,et al.  Sm2Fe17-nitride-based permanent magnets produced by the hydrogenation-decomposition-desorption-recombination (HDDR) process , 1993 .

[9]  K.H.J. Buschow,et al.  New developments in hard magnetic materials , 1991 .

[10]  Satoshi Hirosawa,et al.  The Nd-Fe-B materials for permanent magnets , 1990 .

[11]  G. Schneider,et al.  Analytical TEM study of Al-doped, “two-phase” Nd–Fe–B sintered magnets , 1989 .

[12]  R. Coehoorn,et al.  Permanent magnetic materials based on Nd2Fe14C prepared by melt spinning , 1989 .

[13]  D. B. D. Mooij,et al.  Note on the formation and the magnetic properties of the compound Nd2Fe14C , 1988 .

[14]  J. K. Chen,et al.  On the grain‐boundary phase in iron rare‐earth boron magnets , 1987 .