Quantitative measurement of density in a shear band of metallic glass monitored along its propagation direction

Abstract: Quantitative density measurements from electron scattering show that shear bands in deformed Al_{88}Y_{7}Fe_{5} metallic glass exhibit alternating high and low density regions, ranging from -9 % to +6 % relative to the un-deformed matrix. Small deections of the shear band from the main propagation direction coincide with switches in density from higher to lower than the matrix and vice versa, indicating that faster and slower motion (stick-slip) occurs during the propagation. Nano-beam diffraction analyses provides clear evidence that the density changes are accompanied by structural changes suggesting that shear alters the packing of tightly-bound short- or medium-range atomic clusters. This bears a striking resemblance to the packing behavior in granular shear bands formed upon deformation of granular media.