Instabilities of interfaces between dissimilar metals induced by high pressure torsion

Abstract We observed that high pressure torsion (HPT) of a bi-metallic laminate can induce vortex-like folding instabilities of layers. Thus, HPT leads to multiscale swirls which are perpendicular to the anvil axis. These instabilities are similar to folding of metallic surfaces during sliding and to co-axial swirls by HPT. The HPT induced vortex-like instabilities look very similar to the Kelvin-Helmholtz-type flow instabilities in fluids. We demonstrate in this work that this similarity is only apparent, and physical reasons for HPT-induced instabilituies are principally different from those in liquids. We show using finite element simulations that the folding and vortices of metallic layers are driven by plastic instabilities due to local blocking of shear deformation. Thus, HPT of layered samples leads to the multiscale movement of vortices in the material during deformation. These movements resemble turbulent flow of liquids and gases, but they have a completely different physical nature.