THERMOMAGNETIC ANALYSIS OF NDFEB MELT-SPUN ALLOYS WITH LOW ND CONTENT

The phase transformation of NdFeB melt-spun alloys with low Nd content of 4-8 at. % was investigated by thermomagnetic analysis and x-ray diffractometry. Experimental results have shown that the metastable Nd2Fe 23B3 compound formed in the alloys is considered to be transformed to Nd2Fe23B3+α-Fe+Fe 3B in the temperature range of 550-690°C, α-Fe+Fe 3B+Nd1+eFe4B4 in the temperature range of 690-730°C and finally α-Fe+Nd1+eFe 4B4 above 840°C. From the results, it has been concluded that Nd2Fe14B is not formed from metastable Nd2Fe23B3. On the other hand, the melt-spun alloy of Nd2Fe23B3 (∼Nd 7.1Fe82.1B10.7) annealed under optimum conditions has been found to be composed of α-Fe, Fe3B, and Nd2Fe14B phases. The alloy has a coercivity comparable to Fe3B-based Nd4Fe77B19 and relatively high-energy product of about 71.6 kJ/m3 (∼9 MG Oe). © 1995 American Institute of Physics.