Grain boundary-mediated plasticity accommodating the cracking process in nanograined gold: In situ observations and simulations

In this study, the underlying atomic-scale plastic deformation mechanisms responsible for the crack propagation process in nanograined gold thin film with an average grain size of ~10 nm (ranging from ~2 nm to ~22 nm) is investigated by the in situ high-resolution transmission electron microscope observations (i.e., a homemade device with atomic force microscope inside transmission electron microscope) and atomistic molecular dynamic simulations. The real-time results based on the experimental observations and simulations uncover consistently that the crack propagation in nanograined gold thin film is accommodated by the grain boundary-mediated plasticity, which may result in the grain coalescence between neighboring nanograins. Furthermore, we find that the grain boundary-mediated plasticity is grain size-dependent, i.e., GB dislocation activities-induced grain rotation in relative larger grains and GB migration in relative smaller grains in comparison with a critical grain size of ~ 10 nm.