Effect of mutual substitution of Fe and Ni elements on the plasticity of Fe/Ni-based amorphous alloys: Ab initio molecular dynamics simulations

In order to study the effect of the mutual substitution of Fe and Ni on the plasticity of Fe/Ni-based metallic glasses (MGs) from the atomic arrangement structure perspective, we investigate the short-range order (SRO) and medium-range order (MRO) structures of Fe80P14B6, Fe40Ni40P14B6 and Ni80P14B6 MGs using ab initio molecular dynamics (AIMD) simulations method. The results reveal that Fe40Ni40P14B6 MG has more vertex sharing clusters and less edge-sharing clusters compared to Fe80P14B6 and Ni80P14B6 MGs, indicating that Fe40Ni40P14B6 MG possesses more cavities or boundaries on MRO, which are beneficial for plastic deformation. In addition, large clusters have a relatively strong connection with comparatively smaller clusters in Fe80P14B6 and Ni80P14B6 MGs while the clusters with the similar size tend to form the nearest neighbor in Fe40Ni40P14B6 MG. Compared with the former, the connection mode of the latter may form relatively loose packing, which can facilitate plastic deformation. Fe40Ni40P14B6 MG has larger population of 142 x, 1441 and 1661 bond pairs, which are crystal-like clusters, and relatively smaller 1551and 1541. Besides, Fe40Ni40P14B6 MG has less < 0 0 12 0 >, < 0 1 10 2 > and < 0 2 10 1 > clusters and more < 0 4 4 3 > and < 0 4 4 6 > compared to Fe80P14B6 and Ni80P14B6 MGs, indicating the replacement of Fe by Ni or Ni by Fe in Fe/Ni-based MGs reduces five-fold rotational symmetry, which is beneficial to plasticity.