Individual and collective atomic transportation in deformation of solids at nanoscale

Solids response to stress through deformation. At nanoscale, how the deformation happens and whether the mechanisms can transisit for different length scales, temperatures, and material classes are of high interest for both materials science and nanofabrication techniques such as nanomolding.

In this presentation, we will talk about a transition in deformation mechanisms between individual and collective atomic transportation in solids revealed by thermomechanical nanomolding (TMNM). Specifically, ordered materials (e.g., crystallline metals and alloys) deform through dislocation-slip at high temperature and large size and interface diffusion at high temperature and small size, while disordered materials (e.g., BMGs) transit between viscous flow at large size and interface diffusion at fine scales at temperatures below glass transition. The dislocation-slip and the viscous flow mechanism induce collective atomic motion that maintain the chemical composition of feedstock materials. As a contrast, the interface diffusion mechanism induces atomic motion of each element individually and results in varied chemical composition from feedstock materials through different diffusivities among components. These findings may inspire new insights for research in nanomechanics and materials science and open new possibilities for future nanofabrication techniques.