Crystallization process and kinetics of SmCo/Fe and SmCo/FeCo partially crystallized amorphous alloys

• An insight into phase transformation of SmCo based nanocomposite was given.
• SmCo5 is preferentially precipitated at low temperature in amorphous SmCo/Fe.
• SmCo7 is precipitated at high annealing temperature in amorphous SmCo/Fe.
• The activation energies for SmCo5 and SmCo7 crystallization are 2.5 and 2.8 eV.
• Only SmCo7 is precipitated with activation energy of 2.8 eV in amorphous SmCo/FeCo.

Partially crystallized amorphous alloys SmCo/Fe and SmCo/FeCo with nanocrystalline α-Fe and α-(Fe,Co) grains distributed in the amorphous SmCo matrix were synthesized by mechanical alloying of a mixture of SmCo5 and α-Fe and FeCo powders. The crystallization process and kinetics of these amorphous alloys upon annealing have been investigated. For SmCo/Fe amorphous alloy, with the increase of the annealing temperature to 700 °C, a SmCo5 phase and a SmCo7 phase precipitate in sequence then the SmCo5 transforms to SmCo7. The activation energies for the SmCo5 and SmCo7 crystallization are 2.5 ± 0.1 and 2.8 ± 0.1 eV, respectively. Differently, the SmCo/FeCo amorphous alloy processes only one phase transformation to SmCo7 with an activation energy of 2.8 ± 0.1 eV after annealing to 700 °C. The present study gives an insight into the phase transformation of the SmCo amorphous alloys with different soft phase and is of basic significance to the microstructure controlling of the SmCo based nanocomposite magnets.