Neutron‐scattering investigation of Co‐ and Fe‐based amorphous alloys

Abstract

8.8 alloys were investigated with a time-of-flight small-angle-scattering spectrometer. Also, a structural factor and a total pair correlation function for the amorphous magnetic metallic alloy Co 66 Fe 4 Si 15 B 15 were obtained using the-neutron diffraction method. It was found that cryogenic treatment of the samples (during some hours of conditioning at liquid-nitrogen temperature) affected only the short-range order up to ~1.5 nm, although lowtemperature annealing at temperatures lower than 670 K leads to structural changes at distances larger than 30 nm. The short-range-order change is explained in the framework of structural relaxation. . The relaxation of the microscopic heterogeneity with the change of the short-range topological and chemical order on distances of 0.4-0.7 nm leads probably to the change of the macroscopic properties of AMMAs after the cryogenic treatment [5]. The amorphous metal contains many defects after quenching. The defects result in the distribution of the atomic density and a certain threshold can be considered as vacancies. Such vacancies, defined as a void, are capable of drifting through the alloy by the exchange of the neighbouring atoms [6]. In the amorphous iron model, the potential for the atom shift into the void has a profile of the activation barrier with the void radius above 80 pm. The sharp cooling of the sample allows us to create non-stationary (excess or "frozen") defects because the defect equilibrium conditions change abruptly with temperature. The large number of the non-equilibrium defects increases a self-diffusion velocity [7].In the present work, the properties of amorphous Co-and Fe-based alloys were investigated with neutron diffraction and small-angle scattering. We also observed structural changes of amorphous Fe-and Co-based alloys after cryogenic treatment and low-temperature annealing.