Time-resolved X-ray diffraction study of nanocrystallization in Al-based metallic glasses

Nanocrystallization kinetics of five binary Al-rare earth glassy alloys were investigated in situ using time-resolved X-ray diffraction. From the diffraction spectra parameters the crystalline phase volume fraction and mean crystal size were evaluated. The analysis show that nanocrystal growth kinetics exhibits a sharp transition between extremely rapid and very sluggish growth stage. This observation is supported by the TEM analysis. The nanocrystal size reaches from 9 to 16 nm depending on the alloy system. The crystalline volume fraction approaches 20% from which grain density of about 1.5 × 1023 m−3 is deduced. It is concluded that the nanocrystallization kinetics is governed by nucleation rate and that diffusion controlled growth plays minor role in the devitrification process.