Microstructure evolution at shear bands in superplastic nanophase-separated bulk metallic glass is revealed
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. Therefore, the conditions for formation of shear bands, their structural evolution and multiplication mechanism are extensively studied by many groups using physical experiments as well as computer simulations. In a joint work*, published in Scientific Reports on May 16th, an international team of researchers investigated local conditions at shear bands in new phase-separated bulk MGs containing glassy nanospheres and exhibiting exceptional plasticity under compression. This study provides direct visual evidence for deformation-related effects, in particular increased atomic mobility, in the region around shear bands. 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, which 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 matr
(a) High-resolution TEM micrograph taken at a shear band in deformed Zr59Cu18.15Fe14.85Al8 bulk metallic glass, showing regions of apparent dissolution of the nanospheres (NS) within the band, and coarsening of the nanospheres in the matrix adjacent to the band. (b) Statistical distribution of the nanosphere diameter across a shear band.
For further information contact:
Dr. Ivan Kaban, IFW Dresden; e-mail: i.kaban(at)ifw-dresden.de
Dr. Jie He, Institute of Metal Research, Shenyang, China; e-mail: jiehe(at)imr.ac.cn
Prof. Dr. A. Lindsay Greer, University of Cambridge, UK; e-mail: alg13(at)cam.ac.uk
*Jie He, Ivan Kaban, Norbert Mattern, Kaikai Song, Baoan Sun, Jiuzhou Zhao, Do Hyang Kim, Jürgen Eckert and A. Lindsay Greer. Local microstructure evolution at shear bands in metallic glasses with nanoscale phase separation. Sci. Rep. 6, 25832; URL