Magnetic properties and microstructures of the (SmFe₁₀V₂) _{1 - x}-(Sm₂Fe₁₇)_x cast alloys

The present study shows the magnetic properties of (SmFe₁₀V₂)_{1 - x}-(Sm₂Fe₁₇)_x. cast alloys (x = 0-0.3), The alloys heat-treated below 700 °C show low coercivity but the alloys heat-treated at 800-1000 °C exhibit a relatively high coercivity of around 3 kOe. In particular, the stoichiometric SmFe₁₀V₂ alloy heat-treated at 900 °C for 20 h exhibits the highest coercivity of 3.7 kOe, which is the highest value among the reported values of ThMn₁₂-type magnets in the cast state. This alloy consists of the SmFe₁₀V₂ phase, with grain sizes of several micrometers, and a small amount of the α-(Fe,V) phase. In the alloys heat-treated above 1100 °C, the SmFe₁₀V₂ phase disappears and the α-(Fe,V) phase exists as the major phase. It is considered that the annealing temperature at 1100 °C is higher than the peritectic temperature. The existence of the α- (Fe,V) phase as the major phase is the main reason for the decrease of coercivity.