Density changes in shear bands of a metallic glass determined by correlative analytical transmission electron microscopy

• We describe a novel approach for measuring densities in shear bands of metallic glasses.
• The linear relation of the dark-field intensity I/I0 and the mass thickness ρt was used.
• Individual shear bands showed abrupt contrast changes from bright to dark and vice versa.
• Density changes ranging from about −10% to +6% were found for such shear bands.
• Mixtures of amorphous/medium range ordered domains were found within the shear bands.

Density changes between sheared zones and their surrounding amorphous matrix as a result of plastic deformation in a cold-rolled metallic glass (melt-spun Al88Y7Fe5) were determined using high-angle annular dark-field (HAADF) detector intensities supplemented by electron-energy loss spectroscopy (EELS), energy-dispersive X-ray (EDX) and nano-beam diffraction analyses. Sheared zones or shear bands were observed as regions of bright or dark contrast arising from a higher or lower density relative to the matrix. Moreover, abrupt contrast changes from bright to dark and vice versa were found within individual shear bands. We associate the decrease in density mainly with an enhanced free volume in the shear bands and the increase in density with concomitant changes of the mass. This interpretation is further supported by changes in the zero loss and Plasmon signal originating from such sites. The limits of this new approach are discussed.