Effects of flaw shape and size on fracture toughness and destructive mechanism inside Ni15Al70Co15 metallic glass

The influence of shape and size of flaws on the strain energy, fracture toughness, and brittle to ductile transition mechanisms of Ni15Al70Co15 metallic glass material are carried out in this paper through a simulation of a tensile test. It is found that a less smooth flaw shape has a lower energy absorption capacity per unit volume because the wrinkle of the flaws spends the energy generated during the testing process. The flaw shapes strongly affect the fracture toughness while the flaw sizes decide the dominance in the competition between brittle and ductile fracture/deformation. The deformation forms from stress concentrations at flaw root/the sharp corner of the flaw and develops to the SBs, then shifts to shear transformation zones (STZs) within the small size. However, in the absence of the SBs within the large size of the flaw, the STZs are formed from the deformation embryos leading to display the essential characteristics of ductile fracture. Especially, for a circle flaw specimen with a large radius, the STZs plays a dominant role, leading to ductile fracture.