Plastic Deformation and Size Strengthening of Nanometals

High pressure techniques have been introduced to nanomaterials research for about three decades. Most of the studies, especially in the earlier time, were mainly X-ray diffraction (XRD), Raman and infrared spectroscopy investigations on the structural transition and equation of state. In recent years, we extended the explorations for the plastic deformation of nanomaterials by employing radial diamond-anvil cell XRD and transmission electron microscopy (TEM). We have successfully probed the dislocation activities in 3 nm nanocrystals, but also seen that partial dislocations and deformation twinning dominate the plastic deformation below 20 nm. We have observed the reversal in the grain size dependence of grain rotation in nickel, and have found that the strengthening of nickel nanocrystals could be extended down to 3 nm. Compared with the traditional techniques, high pressure techniques are more advantageous in applying mechanical load to nanosized samples and characterizing the structural and mechanical properties in situ or ex situ, which could help to unveil the mysteries of mechanics at the nanoscale and bridge the knowledge on the material mechanics at the multiscale. With these knowledges, more advanced materials could be fabricated for wider and specialized applications.