Abstract Scope |
Propagations of micro-cracks at grain boundaries (GBs) are investigated in a generic Fe-Ni-Cr model. While keeping all other parameters the same (e.g. crystallography, size, thermo-mechanical stimuli), we control the local chemical orders at GBs via Metropolis Monte Carlo algorithm and then compare the growth of a pre-existing nano-void under cyclic loading in the context of low cycle fatigue. It is found the crack propagates fastest at intermediate level of chemical heterogeneity. In addition, the crack growth is not continuous but instead follows an intermittent pattern, and the abrupt crack advances are driven by the spatial density of those atoms with extreme compressive residue stresses. By examining more general interfaces without pre-existing singularities/cracks, we demonstrate the atomic-level stress variations are non-affine in nature, and the magnitude of non-affine fluctuations also maximizes at intermediate chemical orders. These findings may provide a new perspective towards the understanding of intermediate temperature ductility loss phenomenon. |