Atomic and cluster level dense packing contributes to the high glass-forming ability in metallic glasses

The microstructure features of a representative Zr48Cu45Al7 bulk metallic glass (BMG) were investigated via a series of simulations and calculations coupled with the synchrotron radiation-based experiments. It was revealed that bond shortening occurs in the atomic pairs, due to the strong interaction between the Al dopant atoms and their neighbors. The bond shortening leads to the atomic and cluster level dense packing in the local structures, which should be the structural mechanism of the high glass-forming ability in Al-microalloyed BMGs. This work not only reveals the atomic and cluster level microstructures in this class of glass materials, but also has implications for developing other BMGs with relatively large critical sizes.