Effect of Ga addition on the microstructure and magnetic properties of hydrogenation–disproportionation–desorption–recombination processed Nd–Fe–B powder

Microstructural evolution of hydrogenation–disproportionation–desorption–recombination processed Nd12.5Fe72.8Co8.0B6.5Ga0.2 powder has been investigated in relation to coercivity development during the desorption recombination process. Coercivity increases when residual NdH2 is completely dehydrogenated and the decomposed Nd is segregated at the grain boundaries of the Nd2Fe14B phase. Three-dimensional atom probe (3DAP) analysis indicates the segregation of Ga at the grain boundary. The reason for the enhancement of the coercivity by the trace addition Ga is discussed based on the 3DAP results.