Microstructure, Particle Size, and Magnetic Property of Fe-6.5 wt.% Si Nanocrystalline Alloys Prepared by Mechanical Alloying

Fe-6.5 wt.% Si nanocrystalline alloys with good magnetic softness were prepared by mechanical alloying at various milling times (0–12 h) via a high-energy ball mill. Elemental iron and silicon powders were used as raw materials. Structural evolution, particle size distribution, and magnetic properties were investigated for as-milled Fe-Si alloy powders. During the alloying process, Si atoms dissolve substitutionally into α-Fe lattice, causing a decrease of lattice parameter with the milling time. A single α-(Fe,Si) solid-solution phase with grain size of ~ 10 nm is obtained, and no ordered phases (B2 or DO3) are observed. Ball-milling effectively reduces particle size of the alloy powders from 64 μ m to 30 μ m, and exhibits a controlled distribution of the particle size. A transition in the dominant factor and a deviation from the sixth power law on grain size are confirmed in the coercivity of these Fe-Si alloy powders. Good magnetic softness, with a saturation magnetization of ~ 198 Am 2 /kg and coercivity of ~ 20 A/m, has been achieved. This study validates that mechanical alloying is an effective way to produce single-phase BCC Fe-6.5 wt.% Si alloy powders for applications with magnetic powder cores.