Nanocrystallization of Al92Sm8 amorphous alloy studied in situ by real-time x-ray diffraction

Abstract

We have investigated the in situ isothermal nanocrystallization kinetics of binaryAl92Sm8 glassy alloy using time-resolved x-ray diffraction. From diffraction spectra parameterswe have calculated the mean grain size and crystalline phase volume fraction.The results show that the average grain size does not change by more than15% of its initial value in the course of the nanocrystallization process. The first nanocrystalscontributing to the crystalline phase signal are characterized by a mean crystal size of 11nm which increases up to 13 nm at the end of the primary crystallization stage. Theseresults are in agreement with a TEM analysis. Our observations indicate thevery significant difference in growth rate of small and large clusters. Further,they show that the transformation kinetics is governed by the nucleation rate.We conclude that diffusion controlled growth plays a minor role in the overalltransformation kinetics. Possible origins of the observed crystallization behaviour are given.