Compressive strength of twinned Ni-Co nanoparticles: In-situ experiments and atomistic simulations

Nanoparticles obtained by solid-state dewetting are known to exhibit an extraordinarily high mechanical strength under uniaxial compression. While most of such particles are single-crystalline, some may contain a coherent twin boundary (CTB) parallel to the substrate. The role of the CTB in the mechanical properties of such particles remained unknown. This work combines nano-mechanical testing, advanced characterization methods, and atomistic computer simulations to investigate the CTB effect of the mechanical behavior of Ni-Co nanoparticles produced by solid-state dewetting on a sapphire substrate. The results indicate that the CTB does not make any significant impact on the particle strength, toughness, solute softening, or strain hardening. These properties remain virtually the same as those of single-crystalline particles of the same alloy. The mechanisms of dislocation nucleation and the dislocation-CTB interactions are investigated in detail. The work lends additional confidence to the previous results for the mechanical behavior of nanoparticles produced by solid-state dewetting, some of which could have contained twin boundaries.