A molecular dynamics simulation shows deformation twinning in a tungsten nanocrystal. In conjunction with dislocation slip, the twinning allows nanomaterials to permanently deform without breaking. Computer rendering by Yan Liang.
Transmission electron microscopy (TEM) and computer modeling have combined to produce an understanding of how atomic-scale deformation mechanisms determine the structure and properties of nanomaterials. Researchers from Georgia Tech, the University of Pittsburgh, and Drexel University engineered a new way to observe and study these mechanisms.
Deformation twinning is a type of deformation that, in conjunction with dislocation slip, allows materials to permanently deform without breaking. In the process of twinning, the crystal reorients, which creates a region that is a mirror image of the original crystal.
In research reported in the journal Nature Materials, the Pittsburgh researchers observed atomic-scale twinning in the material tungsten by welding together two small pieces of the material to create a wire about 20 nanometers in diameter. This wire was durable enough to stretch and compress while being observed using high-resolution TEM.
Ting Zhu, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, studied the process from a different perspective, using molecular dynamics simulation to view the deformation in three dimensions.
“If you reduce the size to the nanometer scale, you can increase strength by several orders of magnitude,” Zhu said. “But the price you pay is a dramatic decrease in the ductility. We want to increase the strength without compromising the ductility in developing these nanostructured metals and alloys. To reach this objective, we need to understand the controlling deformation mechanisms.”
— Joe Miksch, University of Pittsburgh
