An investigation of the Nd-rich phases in the Nd-Fe-B system

Abstract

The crystal structures and the compositions of the Nd-rich phases in the Nd-Fe-B system have been investigated by means of transmission electron microscopy, x-ray diffraction, and Auger spectroscopy techniques. It has been observed that there are two kinds of Nd-rich phases with different structures and compositions. Most of the Nd-rich phases will undergo a phase transformation when the powder is sintered at high temperatures. This phase transformation is accompanied by the introduction of oxygen into the alloy which will change from a ternary system into a quaternary one. Both of the two Nd-rich phases are stable phases in this later system. With the aid of the EDX and the Auger spectroscope, the compositions of the dhcp and the fcc Nd-rich phases have been determined. The Nd contents of the two phases are about 90 and 70 at. %, respectively, with the later phase containing about 15 at. % of oxygen.