EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

When metallic glasses are deformed under a compressive stress state, it is often found that pressure-induced phase transformation under hydrostatic pressure. The relationship between the equivalent stress and stress triaxiality is well described by the Mohr-Coulomb criterion, and the stress triaxiality has a linear relation with the hydrostatic pressure. During cyclic deformation non-uniaxial stress numerically postulated in amorphous systems, the amount of strain increases with increasing deformation and distribution of effective strain is significantly changed at near surface region by accumulated deformation passes. When the shear band conditions approach from uniaxial to constrained multi-axial stress conditions, then strain energy-driven atomic diffusion can be induced plastic flow of materials. The deviation of the shear plane away from the maximum shear direction is an indication that the flow process of the material has a dependency on the normal stress acting on the shear plane. Moreover, the equivalent strain to failure differs quite significantly for specimens under different stress triaxialities. The numerical calculation results by finite element method (FEM) revealed that the stress triaxiality differs between the compressive surface and the lateral surface during compression or rolling. Distribution of effective strain is significantly changed at near surface region of Hf-based metallic glass disc with increasing rolling pass.