Ga added Nd-Fe-B sintered and die-upset magnets

The addition of Ga to Nd-Fe-B sintered and die-upset magnets in order to improve thermal stability was examined. The Ga addition increases the coercivity of Nd(Fe_0.72Co_0.2B_0.08)_5.6 sintered magnets markedly. Ga addition does not enhance coercivity of sintered magnets with lower Co substitution. Ga addition increases coercivity for Nd-Fe-B die-upset magnets. No decrease in coercivity due to Co substitution of up to 20 at.% is observed for Nd₁₄Fe _79.25B₆Ga_0.75 die-upset magnets. This is an advantage of the die-upset magnets compared with the sintered magnets. Ga has a tendency to occur in the Nd-rich phase at higher concentrations than 2 wt.%, and Ga content in the 2/14/1 matrix is around 0.2 wt.% for Nd₁₄Fe_79.25BGa_0.75 die-upset magnets. For sintered magnets, Ga is distributed between the matrix and the Nd-rich phase. H_A of the 2/14/1 matrix is increased by Ga addition up to 2.5 at.%. The correlation between H_A and iH_c is not good. The Ga-containing Nd-rich phase is observed in the sintered magnets, and the role of Ga in this phase needs to be evaluated to understand coercivity enhancement by Ga addition