At room temperature, plastic flow of metallic glasses (MGs) is sharply localized in shear bands, which are a key feature of the plastic deformation in MGs. Despite their clear importance and decades of study, the conditions for formation of shear bands, their structural evolution and multiplication mechanism are still under debate. In this work, we investigate the local conditions at shear bands in new phase-separated bulk MGs containing glassy nanospheres and exhibiting exceptional plasticity under compression. It is found that the glassy nanospheres within the shear band dissolve through mechanical mixing driven by the sharp strain localization there, while those nearby in the matrix coarsen by Ostwald ripening due to the increased atomic mobility. The experimental evidence demonstrates that there exists an affected zone around the shear band. This zone may arise from low-strain plastic deformation in the matrix between the bands. These results suggest that measured property changes originate not only from the shear bands themselves, but also from the affected zones in the adjacent matrix. This work sheds light on direct visualization of deformation-related effects, in particular increased atomic mobility, in the region around shear bands.
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Financial support for this research is gratefully acknowledged: for J.H. from the Alexander von Humboldt Foundation, the National Natural Science Foundation of China (Grant No. 51374194 and 51574216) and the Natural Science Foundation of Liaoning Province of China (Grant No. 2015020172); for J.E. from the German Federal Ministry of Education and Science (Project No. 05K12OD1), the German Science Foundation under the Leibniz Program (Grant EC 111/26-1) and the European Research Council under the ERC Advanced Grant INTELHYB (Grant ERC-2013-ADG-340025); for D.H.K. from the Global Research Laboratory Program of the Korean Ministry of Education, Science and Technology; and for A.L.G. from the Engineering and Physical Sciences Research Council (UK) and the World Premier International Research Center Initiative (WPI), MEXT, Japan.
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