Preparation of high performance bulk Fe–N alloy by spark plasma sintering.

Bulk Fe–N alloys were fabricated using ultra-fine ε-Fe 3 N powder by spark plasma sintering (SPS) at 600 °C, 650 °C, 700 °C, and 750 °C. The sintering temperatures were varied over wide ranges and the impact of such variations on sintered specimens was investigated through the characterization of their microstructures, chemical compositions, hardness, densities, compressive properties, and magnetic properties. The results indicate that γ ′-Fe 4 N and α -(Fe,N) (Fe–N solid solution) are the major phases of sintered specimens and the nitrogen concentration can significantly reduce with the sintering temperature increasing. The Fe–N phase transformation behavior during sintering process influences the instantaneous density, microstructure, and properties. The γ ′-Fe 4 N and α -(Fe,N) formed an homogeneous multiphase structure in the specimen sintered at 700 °C and this structure shows excellent compressive properties. Specimens sintered at 750 °C possess higher toughness, larger saturation magnetization, lower coercivity, and less remanence ratio. These findings indicate a certain nitrogen concentration bulk Fe–N alloy with good performance is attainable via SPS. [ABSTRACT FROM AUTHOR]