EVOLUTION OF PHASES AND MICROSTRUCTURE IN FE81B13.5SI3.5C2 METALLIC-GLASS DURING ELECTRON-BEAM AND PULSED-LASER IRRADIATION

A comparative study of electron-beam and pulsed-laser irradiation effects in metallic glasses has been performed in order to understand the relationship between magnetic behavior and select variations in the structural characteristics of alloy phases. Samples of Fe81B13.5Si3.5C2 metallic glass were irradiated with a pulsed excimer laser (λ=308 nm, τ=10 ns), with a high-energy electron beam (W=7 MeV), and with low-energy electron beams (W=30 and 50 keV). Irradiation-driven changes in the magnetic anisotropy and phase equilibrium of alloy samples were studied by Mössbauer spectroscopy and scanning electron microscopy. Complementary information was obtained using energy-dispersive x-ray analysis. High-energy electron-beam irradiation was found to induce an out-of-plane magnetic anisotropy due to changes in the chemical short-range order. Low-energy electron-beam irradiation resulted in the formation of crystalline regions, in which α-Fe, Fe-Si, Fe3B, Fe2B, and clusters of γ-Fe were identified. Interpretation of these results is given in terms of radiation-enhanced diffusion. Pulsed-excimer-laser irradiation was found to induce controlled magnetic anisotropy without onset of bulk crystallization in the Fe81B13.5Si3.5C2 amorphous system. The effect of excimer-laser-induced amorphization was evidenced in thermally annealed Fe81B13.5Si3.5C2 samples and explained using melt model calculations. In all cases studied, the key to explaining the irradiation-induced property modifications is the underlying alloy microstructure. © 1995 The American Physical Society.