High-energy ball-milling synthesis and densification of Fe–Co alloy nanopowders by field-activated sintering (FAST)

Nanocrystalline Fe–Co soft magnetic alloy powders also containing approximately 4% Cr and 1% V were prepared by high-energy mechanical alloying in liquid media (hexane). Bulk nanostructured magnets of 40 mm diameter were obtained by field-assisted sintering (FAST) also known as spark-plasma sintering (SPS). We used a FAST furnace type HPD25-1 (FCT Systeme, Rauenstein, Germany). The FAST method was shown to successfully assist in decoupling densification from microstructural coarsening, mainly due to the limited exposure of the alloy nanopowders to high temperatures during their sintering into nanostructured bulk compacts. Results of chemical and microstructure analysis by SEM/EDX are presented to evidence the achievement of uniform microstructures and absence of composition gradients across sintered bulk specimens in spite of their large size.