Effect of pre-existing shear bands on mechanical properties and serration behaviors in bulk metallic glasses

Pre-existing（multiple）shear bands were introduced into the ductile Zr56Co28Al16 and Zr65Ni10Cu15Al10bulk metallic glasses（BMGs）through the lateral-deformation,respectively.It was found that the pre-exiting shear bands can further enhance the compressive plasticity of ductile BMGs.According to the serration analysis on the plastic deformation of the as-cast and the pre-deformed samples,the serration events in the stress-strain curves during deformation display a self-organized critical（SOC）behavior.Compared with the as-cast BMGs,a larger power-law scaling exponent calculated based on serrated flow behaviors becomes larger for the pre-deformed BMGs,implying that the shear banding stability of BMGs is effectively enhanced.This should be caused by the pronounced interactions of shear bands during plastic deformation for the pre-deformed BMGs.However,by introducing a large amount of multiple shear bands into the glassy matrix,it also becomes easier for shear bands to propagate along the pre-existing shear bands,leading to a lower cut-off elastic energy density for the pre-deformed BMGs.More multiple shear bands with stronger interactions for the pre-deformed BMGs could provide a larger chance to activate the shear-band cracking but less local elastic energies are remained for the subsequent crack-linking.