Region selectivity of nanometer scale crystallization behavior in metallic glass

It has been known that the internal structure of metallic glass is composed of elastic region and fragile region. However, it is not clear whether the distribution of these regions has an effect on the occurrence of crystallization behavior. Here, the molecular dynamics simulation is employed to investigate the nanometer scale crystallization behavior in metallic glass. A regional selective characteristic is revealed for the occurrence of crystallization behavior in the metallic glasses, which is different from that in the melt, showing the unique nature of crystallization behavior in amorphous system. It is observed that the crystallization behavior occurs first in the elastic region dominated by the icosahedral network, rather than in the fragile region dominated by the low-population polyhedron. This phenomenon can be attributed to that the Gibbs free energy barrier between the BCC structure and the low-population polyhedron in the fragile region is higher than the free energy barrier between the BCC structure and the icosahedral network.