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A density variation in shear bands visible by electron microscopy is correlated with compositionally altered locations measured by atom-probe tomography in plastically-deformed Al85.6Y7.5Fe5.8 metallic-glass ribbons. Twocompositionally distinct regions are identified along shear bands, one is Al-rich (~92 at.%), the other is Al depleted(~82.5 at.%) and both regions show marginal concentration fluctuations of Y and Fe. The elementalre-distribution is observed within shear bands only, and no chemical exchange with the surrounding glassy matrixis observed. Macroscopic deformation of metallic glasses (MGs) is mainly confinedto shear bands (SBs), which limits the ductility to often less thana fewpercent intension[1–6].Much effort has been devoted to enhancethe ductility by controlling SBs initiation and propagation [7–18]. Due tothe key role of SBs in the deformation, better understanding of theirstructure and chemical composition is of interest. Transmission electron microscopy (TEM) has been extensively usedto study the underlying mechanisms of vitrification and nanocrystallizationin Al-based MGs [19–22] in order to obtain glass/crystalcomposites with enhanced ductility [23,24]. High-angle annular darkfieldscanning TEM(STEM-HAADF) has revealed a periodic spatial variationof dark and bright regions of intensity along thin SBs in plasticallydeformedAl88Y7Fe5 [7], Pd40Ni40P20 [8] andZr52.5Cu17.9Ni14.6Al10Ti5 [25]MGs (all compositions are given in at.% throughout the text). Since thedark field intensity corresponds to a resultant atomic (Z) contrast, theobserved periodic variations can originate from the combination oflocal compositional and mass-density fluctuations. The variationswere also observed for Zr-, Pd- and Mg-based MGs [26] by a synchrotronX-ray tomography. For an Al88Y7Fe5 MG ribbon, cold-rolled to~28% thickness reduction, mass-density changes between −9% and+6% and an average fluctuation length of ~50–110 nm in b10 nmthick SBs were observed [7]. Periodic-density fluctuations along SBswere also reported for cold-rolled Pd40Ni40P20 MGs with up to 20%thickness reduction [8]. Some reports correlate the fluctuations to ahigh volumetric strain during SBs formation [11]. Although the structureof SBs has been described by atomistic simulations [27–29], it is unclearwhether density variation inside SBs is a generally-observedphenomenon. Unlike the observations reported in Ref. [8], no densityfluctuations inside SBs were observed in Pd40Ni40P20 bulk MGs compressedto an engineering plastic strain of 0.4 [30]. Despite the effortsto characterize the local low- and high-mass-density variations in SBsfor Al88Y7Fe5 glass, the corresponding compositional changes have notbeen rigorously analyzed except by Rösner et al. [25] using STEMenergy-dispersive spectroscopy (STEM-EDS). Nevertheless, varying foil thickness and a projection plane of SBs in the EDS analyzed volumecauses practical challenges to accurately quantify the composition insideSBs, which are clearly visible in the edge-on perspective only, andhence characterizing 3-D aspects of the elemental re-distribution bySTEM is difficult.Atom-probe tomography (APT) enables quantitative 3-D compositionalanalysis with the near atomic resolution with equal sensitivityin the range of 10 ppm for all elements [31], which makes it an idealprobe for chemical changes associated with SBs. Typically, APT hasbeen used to study solute partitioning [32], vitrification and crystallization [33,34] in Al-basedMGs. There have been relatively a fewattemptsto investigate both, the mass-density and the compositional fluctuationsalong SBs by APT. Hunter et al. [35] studied the origin of SBs initiationin a Ti-based glass/nanocrystalline composite and they observedno compositional fluctuations along SBs. For APT technique, theatomic-density and spatial resolutions are prone to artifacts due toion-trajectory aberrations and local magnification effects. It has beenargued that the apparent density change observed in SBs by APT couldbe an artifact due to the local lowering of the evaporation field at SBs positionsin a tip [35]. The presence of such aberration effects forbids to unambiguouslylocate SBs in terms of APT alone, especially when thechemical variations inside SBs and relative to the adjacent matrix aresubtle. In this paper, a combined TEM/APT characterization [36] is appliedto directly correlate density fluctuations along SBs visible bySTEM with chemical alterations analyzed by APT.