OBSERVATION OF MINOR MAGNETIC PHASES IN AS-CAST ND2 (FE1-XALX)14B-BASED AND RELATED ALLOYS

The presence of minor magnetic phases in as-cast Nd80Fe15B5, Nd21Fe73. 5B5.5 and Nd16(Fe1-xAlx)76B8 (0.0 less-than-or-equal-to x less-than-or -equal-to 0.15) permanent magnetic alloys has been investigated. Magne tic phases having a Curie temperature of 245-degrees-C (A1 metastable phase), 292-degrees-C (A3 phase) and 170-degrees-C (M1 phase) were obs erved in Nd-Fe-B and Nd-(Fe, Al)-B alloys, respectively. An analysis p erformed on Nd85(Fe1-xAlx)15 (0.0 less-than-or-equal-to x less-than-or -equal-to 0.7) alloys suggested that M1 is an Al-doped A1 phase. In in teraction with the 2:14:1 boride such metastable phases could act as c enters for magnetization reversal at lower fields, their dissolution m ust be considered among the factors that explain the beneficial effect on coercivity of the post-sintering annealing at 600-degrees-C in sin tered magnets.