Atomic Structure Design of Rapidly Quenched Amorphous Cobalt-Based Alloys

The research presents the atomic structure investigation of amorphous rapidly quenched Co58Ni10Fe5Si11B16 at.% alloys. The alloys were quenched with linear velocity of cooper wheel surface from 22 to 38 m/s. We found a nonlinear dependence of local atomic ordering from linear velocity of cooling wheel. The average lateral density of ordered atomic clusters of 5 nm size changes from 4% to 8%. The amorphous alloy with metastable disordered structure with lower level of free energy is more stable against the external conditions. This approach can be used to determine the best technological parameters for preparing amorphous metallic alloy with metastable structure.

Diffusion-Controlled Nanocrystallization of the Fe73.5Cu1Nb3Si15.5B7 Finemet Amorphous Alloy

Crystallization of the amorphous metallic alloy Fe73.5 Cu1Nb3 Si8.5 B14 was investigated by ferromagnetic resonance (FMR), small angle in situ X-ray scattering (SAXS/WAXS) and differential scanning calorimetry (DSC). Only one crystalline phase was observed by WAXS and only one peak was observed by DSC. The activation energies, calculated from FMR and DSC data, were 287 kJ.mol-1 and 313.4 kJ.mol-1, respectively. The values calculated for the Avrami exponent were 0.98 (FMR) and 1.4 (DSC). These values correspond to different mechanisms of nucleation and growth; however, the SAXS /WAXS results suggest that the dominant mechanisms are nucleation and growth of crystals from small dimensions.