Modulating strengthening ability of layer-grained fcc metals with distinct stacking fault energy: Molecular dynamics simulation

The limited ductility of nanocrystalline metals severely hinders their practical applications due to the absence of strain hardening. In this study, we observed strain hardening in layer-grained models through molecular dynamics simulations. Our quantitative analysis demonstrated that grain boundary deformation induced strain hardening, while dislocation activities led to strain softening. This finding is fundamentally different from previous assumptions that dislocation activities cause strain hardening, whereas grain boundary deformation can lead to strain softening. The competition between grain boundary deformation and dislocation activities determines the strain hardening behaviors in nanocrystalline metals. By modifying the stacking fault energy and tailoring lamellar grains, it is possible to increase the proportion of grain boundary deformation and achieve good ductility in strong nanocrystalline metals. Such metallic materials with high strength and good ductility, hold great potential for a wide range of industrial and engineering applications.