Investigation on the inhomogeneous structure of metallic glasses based on the initial elastic deformation in nanoindentation

The initial elastic deformation of bulk metallic glasses (BMGs) with various casting diameters and annealing conditions was investigated by nanoindentation test with a spherical indenter. It was found that with the increasing of the glassy rod diameter and the annealing temperature, the onset slope of nanoindentation plot remarkably increased. The BMGs with various casting diameters and annealing temperatures are of different atomic configuration due to their different cooling rate during casting and different structural relaxation processes during annealing, respectively, indicating that the onset slope of nanoindentation plot is strangely dependent on the atomic configuration. Therefore, the onset slope of nanoindentation plot may serve as an indicator of the initial deformation behavior of BMGs. The structual origin of the initial elastic deformation was discussed in terms of short order nature in glasses and the distribution of free volume.

► The onset nanoindentation slope increases with the BMG diameter.
► The onset nanoindentation slope increases with the annealing temperature.
► Free volume decreases with the increase of diameter and annealing temperature.
► The initial elastic deformation reflects the cluster bonding characteristic.
► Cluster bonding characteristic is significant in understanding BMG’s properties.