Role of Fragility of the Glass Formers in the Yielding Transition under Oscillatory Shear

Metallic glasses are widely used amorphous materials known for their exceptional mechanical properties, such as high yield strength and large yield strain. Understanding the microscopic mechanisms behind their failure, particularly the yielding transition, remains an active area of research. Previous studies have shown that yielding behavior depends on the initial age of the sample. Through extensive computer simulations, we demonstrate that this age dependence varies across different materials and is influenced by the specific characteristics of the initial glass former, particularly its fragility. Both strong and fragile glass formers exhibit similar behavior in poorly annealed conditions, but the yield point increases significantly with annealing for fragile glasses while remaining relatively constant for strong glasses. We rationalize these findings by introducing a new elastoplastic model, which qualitatively reproduces the simulation results and offers valuable insights into the physics of the yielding transition under oscillatory shear deformation.