Shear banding mechanism in compressed nanocrystalline ceramic nanopillars

Abstract

Shear banding causes deformation to be heavily restricted in small volumes of a material, leading to catastrophic failure of materials. Yet how shear bands form is generally not known. Here, the authors follow the entire process of shear banding in the nanocrystalline ceramic (NCC) nanopillars of ZrN using $i\phantom{\rule{0}{0ex}}n$ $s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}u$ microscopy. The evidence obtained shows that the nanopillars deform through intermittent granular activities due to the nucleation and propagation of dislocations. The stress drops associated with these activities, however, are small as dislocation avalanches are restricted by the nanograin size. Shear band forms in NCC through localized and cooperative granular activities involving nanocrack formation.