Devitrification of Al-based glass forming alloys

Al88Y7Fe5 samples were rapidly quenched into a fully amorphous state. Calorimetric investigations together with X-ray diffraction analyses show that a primary crystallization of Al-nanocrystals occurs at the onset temperature of 276 °C. Isothermal annealing treatments that were performed for different times at temperatures well below the primary crystallization onset observed during rate heating show that Al-nanocrystals develop after short periods. Moreover, these investigations indicate the formation of a transient phase that formed at higher temperatures only after annealing at lower temperatures for intermediate time intervals. Additionally, HRTEM analyses show a fringe structure in the matrix surrounding the nanocrystals that corresponds to the transient phase crystallites. The results are discussed in the context of nucleation in the presence of concentration gradients at the nanocrystal/glass interface.