Magnetic hardening of mechanically alloyed NdFe 12− xV x (1⩽ x⩽2) and their nitrides

Abstract

The structure and permanent magnetic properties of isotropic powders of NdFe 12− x V x N δ compounds were investigated by using mechanical alloying. It was found that heat treatment of as-milled powders at 700–900°C resulted in the formation of Nd(Fe,V) 12 phase except for the sample with x=1, for which the crystallization was not complete and a large amount of α-Fe(V) was present at temperatures lower than 750°C. After nitrogenation, the volume expansion was about 5% and the Curie temperature enhancements were 140 to 160°C. In NdFe 12− x V x N δ the values of T c fall in the range 469–485°C. It has been found that the intrinsic coercivities strongly increased with increasing V content. The maximum coercivity of i H c=10.96 kOe is achieved at 750°C with x=2.00. The difference between the coercivities of the mechanical alloyed Nd(Fe,V) 12N δ powders with different V content is attributed to their different crystallization behavior and phase stability during nitrogenation.