  Minor alloying is widely used to control mechanical properties of metallic
glasses (MGs). The present understanding of how a small amount of alloying
element changes strength is that the additions lead to more efficient packing
of atoms and increased local topological order, which then increases the
barrier for shear transformations and the resistance to plastic deformation.
Here, we discover that minor alloying can improve the strength of MGs by
increasing the chemical bond strength alone and show that this strengthening is
distinct from changes in topological order. The results were obtained using
Al-Sm based MGs minor alloyed with transition metals (TMs). The addition of TMs
led to an increase in the hardness of the MGs which, however, could not be
explained based on changes in the topological ordering in the structure.
Instead we found that it was the strong bonding between TM and Al atoms which
led to a higher resistance to shear transformation that resulted in higher
strength and hardness, while the topology around the TM atoms had no influence
on their mechanical response. This finding demonstrates that the effects of
topology and chemistry on mechanical properties of MGs are independent of each
other and that they should be understood as separate, sometimes competing
mechanisms of strengthening. This understanding lays a foundation for design of
MGs with improved mechanical properties.
