In metallic nano-glasses (NGs), the atomic structures of interiors of glassy grains are similar to those of bulk metallic glasses, while the viscous glass-glass interfaces (GGIs) are less dense and could be in a thermodynamically unstable glass state, loosely bonding the adjacent glassy grains and notably reducing the mechanical strength of NGs. It has been previously established that multicomponent alloys containing five or more principal elements tend to be thermodynamically stable, largely due to the high entropy of mixing. Similarly, glass phase of GGIs may be stabilized as entropy of mixing in the GGI regions increases, consequently strengthening the NGs. In this study, multicomponent metallic NGs are investigated to address the issues related with entropy-stabilized GGIs. Analyses on the thermodynamic properties of metallic NGs reveal that the increase in entropy of mixing leads to the stabilization of GGIs, which are in a new glass phase different with that of interiors of glassy grains. The mechanical properties of metallic NGs are further examined by nanoindentation, micro-pillar compression and creep tests under tensions, showing that the entropy-stabilized GGIs are responsible for enhancing the mechanical properties of metallic NGs. Theoretical modeling on the influences of structural and compositional heterogeneity in multicomponent metallic NGs on their mechanical properties is carried out by molecular dynamic (MD) simulation and kinetic models of inhomogeneous plastic flows in metallic glasses. As elucidated by the MD simulation, the preference of shear banding in the GGI regions with a particular GGI incline angle originates from the composition heterogeneity in the GGI regions. The kinetic model of inhomogeneous plastic flows suggests that the metallic NGs can achieve higher toughness or plasticity by blocking the extension of the multiple, short, local shear zones or bands through the GGI regions to the interiors of glassy grains with relatively low free-volume densities. 

Dr. Guangping Zheng is currently an Associate Professor in Department of Mechanical Engineering at the Hong Kong Polytechnic University. His research areas are computational materials science, nanomechanics, mechanical properties and deformation mechanisms of bulk metallic glasses, metallic nano-glasses and high-entropy alloys. He has published more than 240 papers in refereed journals.