Shear band evolution and deformation behavior of various metallic glass-forming alloys in bending mode

Abstract

In the present study we try to understand and characterize the shear band nature for various metallic glasses under different strain rates. We carefully evaluated the relationship between Kink angle (amount of plastic deformation) and estimated strain rates in various metallic glasses through the bend test of ribbon samples. The samples were bended between two platens in the bending machine with various platen speeds. After recovering curvature of ribbon sample the remaining kink angle of ribbon sample was measured by optical microscope. The different degree of kink angle is closely related to shear band density. For example, at higher estimated strain rate, less plastic deformation occurs, implied by smaller kink angle (fewer number of shear bands), while at lower estimated strain rate, higher plastic deformation occurs implied by greater kink angle (higher number of shear bands) of the ribbon sample. The kink angles of various metallic glasses were also evaluated at same estimated strain rate. In relatively brittle metallic glass, deformed region is relatively small with local generation of shear bands with larger shear step height, while in relatively ductile metallic glass the deformed region is large with widely spaced shear bands with small shear step height. These results give us not only information on the deformation tendency depending on the deformation variables but also clues to understand the deformation mechanism of various metallic glasses.