Atomic structure evolution in metallic glasses under cyclic deformation

Because of the limited experimental capability as well as computing power, the understanding of atomic structure evolution in metallic glasses (MGs) under cyclic loading is still lacking, which in turn makes the fatigue mechanism of MGs remaining largely elusive. Here we perform molecular dynamics simulations of tension-compression fatigue tests in Cu50Zr50 MGs under strain-controlled cyclic loading. When the applied strain lies in the elastic regime, no noticeable changes in the atomic structure of MGs in terms of pair distribution function and the fraction of various Voronoi polyhedra have been found during fatigue tests. When the applied strain lies in the plastic regime, however, shear band (SB) thickening is the intrinsic fatigue mechanism for MGs. It is shown that after its formation, the SB does not propagate along the shearing plane or develop into fatigue cracks with further cyclic loading. Instead the SB expands spatially and eventually evolves into the soft second phase with increased free volume within. The present study provides an in-depth atomic understanding of the structural evolution in MGs under low-cycle fatigue deformation.