Structure, phase transformation and magnetic properties of Nd-Fe-C alloys made by mechanical alloying and subsequent annealing

Structure, phase transformation and magnetic properties of mechanically alloyed (MA) NdyFe100-1.5yC0.5y, Nd16Fe84-mCm and NdnFe92-nC8, alloys depend sensitively on the compositions and the annealing temperatures. Nd2Fe14C can be formed by a solid state reaction of α-Fe with Nd2C3 as well as by a reaction of Nd2Fe17Cx with Nd-C compounds. The thermal stability of Nd2Fe14C increases with the increase of carbon content, reaches a maximum and then decreases. Nd2Fe14C is stable in a triangular shaped area in a status diagram with axes of annealing temperature and composition. To make Nd2Fe14C the main phase, the Nd:C ratio must be kept within a certain range, because too little carbon leads to Nd2Fe17Cx as the main phase, and too much carbon increases the α-Fe content, inhibiting the formation of Nd2Fe14C. (orig.)