Atomistic investigation of the intrinsic toughening mechanism in metallic glass

Metallic glasses (MGs) can have high fracture toughness by carefully choosing chemical compositions. However, their intrinsic toughening mechanism is vital but mysterious. In this paper, large scale molecular dynamic simulations are conducted to study the fracture behavior and underlying mechanism of MGs from atomistic points of view. By changing the composition ratios, the fracture behavior of the MGs transits from void nucleation and coalescence to shear bands toughening. Uniformed local atomic number density is found to be responsible for the high toughness while highly fluctuated local atomic number density result in cavitation governed brittle fracture. The strength of the ductile MGs is more sensitive to the initial void compared with the brittle ones due to the different fluctuations in atomic structures. In the simulations, it is also found that the ductile MGs have a higher Poisson's ratio which may also improve the toughness. The obtained results shed light on the effect of chemical compositions upon the toughness of MGs. (C) 2016 Elsevier B.V. All rights reserved.