Analysis of nanocrystallization process of amorphous Al90Y10 alloy

The nanocrystallization behavior during isothermal annealing of amorphous Al 90 Y 10 ribbons was investigated by means of electrical resistivity measurements, transmission electron microscopy (TEM) and X-ray diffractometry. The fcc-Al nanocrystals content versus annealing time was calculated from isothermal resistivity experiments. X-ray measurements provided information on fcc-Al(111) peak parameter changes during the first stage of crystallization process. The mean grain size was calculated from peak broadening using the standard Debye-Scherrer equation. The experimentally determined time evolution of crystal radius was modeled taking into account overlapping diffusion fields (soft impingement). Heterogeneous nucleation was found as a dominant mechanism of the first stage of a transformation. A small amount of homogeneous nucleation was also identified from the shape of the grain size distribution calculated from TEM micrograph. Grain size and grain density values obtained from TEM were compared to the transformed volume fraction obtained from the resistivity on time dependencies. This implies that a majority fraction of grains is not observable by TEM due to lack of crystals contrast against the one of amorphous matrix.