Investigating the Possibility of Fabricating Pr2Fe14B/α-Fe Composite Materials by Oxidation of the Pr–Fe–B Alloy in a Fluidized-Bed Jet Mill

The results of studying the possibility of fabricating the Pr 2 Fe 14 B/α-Fe composite materials by oxidation of the Pr–Fe–B alloy in a fluidized-bed jet mill are presented. It is shown that the use of the standard powder metallurgy technology supplemented by oxidation of the Pr–Fe–B alloy in a fluidized-bed jet mill for rare-earth magnetically hard materials (MHMs) makes it possible to fabricate Pr 2 Fe 14 B/α-Fe composites with high magnetic characteristics. It is established that, when fabricating finely dispersed powders according to the proposed technology in the argon medium containing 0.2 vol % oxygen, residual magnetic induction ( B r ) occurs with an insignificant drop in the coercive force ( jH c ). This effect causes a 5% increase in the maximal energy product ( BH ) max . The almost complete oxidation of the highly praseodymium phase Pr x Fe occurs with a further increase in the oxygen concentration, which leads to an abrupt drop in the coercive force and, consequently, a decrease in ( BH ) max . The particles of the α-Fe phase formed due to the oxidation of the magnetic material are formed at the boundaries between the grains of the Pr 2 Fe 14 B phase. Herewith, the highest magnetic characteristics are implemented if the α-Fe particles are separated from the grains of the main magnetic phase by thin interlayers of nonmagnetic phases, which makes it possible to hold a high level of jH c for sintered MHM samples. Herewith, the optimal thickness of the α-Fe layers is 0.2–0.3 μm. The α-Fe layers formed with an oxygen content of 0.3 vol % turned out considerably thicker (from 0.8 to 1.1 μm), which leads to an almost 10% decrease in the coercive force of the samples and 3–7% decrease in other magnetic parameters ( B r , ( BH ) max ). Thus, when controlling the oxygen content in the working medium of the jet mill, we can vary the thickness of the interlayer of the forming α-Fe phase in the Pr 2 Fe 14 B/α-Fe composite material and control its magnetic parameters.