Tuning local structures in metallic glasses by cooling rate

The Zr48Cu45Al7 amorphous alloy samples quenched under cooling rates of about 2 × 106 K/s and 1 × 102 K/s were prepared by melt spinning and copper-mold suction casting, respectively. Synchrotron-radiation based experiments, combined with a series of calculations, were performed to study the microstructures in both samples. It was found that although the short-range orderings are similar in Zr-centered clusters for both samples, the atom arrangements and distributions in Cu- and Al-centered clusters are very different in terms of atomic-packing efficiencies and regularity of clusters in these two samples. A quantitative analysis revealed that the lower cooling rate leads to the higher packing efficiency and the higher regularity of clusters. This revealed how the cooling rate during quenching fine-tunes the atomic- and cluster-level microstructures in amorphous alloys with the same composition, which may be the structural basis to address the issue why macroscopic properties change with the cooling rate.