EFFECT OF CR-DOPING ON CRYSTALLIZATION SEQUENCE AND MAGNETIC-PROPERTIES OF FE3B ND2FE14B NANOCOMPOSITE PERMANENT-MAGNETS/

Crystallization sequence starting from NdxFe82-xB18 and NdxFe79-xCr3B1 8(x=3.5-5.5 at%) amorphous alloys has been investigated using X-ray di ffractometer. In the alloys with Nd concentration around 5 at%, the in termediate compound Nd2Fe23B3 first crystallizes along with Fe3B from the amorphous state. Then, the Nd2Fe23B3 phase decomposes to form a mi xture of Nd2Fe14B, Fe3B and alpha Fe for the Cr-bearing systems, where as it breaks up into another mixture of ape and NdFe4B4 for the Cr-fre e systems. Atom probe field ion microscopy analysis has revealed that Cr is preferentially partitioned into the Fe3B phase during the crysta llization process, which may stabilize the Fe3B-containing mixture exh ibited in the Cr-doped systems. We can conclude that a large fraction of Nd2Fe14B produced from the distinct decomposition scheme of the int ermediate Nd2Fe23B3 phase exhibited in the Cr-doped systems brings abo ut the high coercivity materials. (C) 1998 Acta Metallurgica Inc.