Dresden 2017 – wissenschaftliches Programm
MM 39: Topical session: Interface-Controlled Microstructures: Mechanical Properties and Mechano-Chemical Coupling - Structure and deformation III
MM 39.4: Vortrag
Mittwoch, 22. März 2017, 11:00–11:15, IFW B
Interfaces and Vortices under High Pressure Torsion — •Roman Kulagin1, Yulia Ivanisenko1, Yan Beygelzimer2, Andrey Mazilkin1,3, Boris Straumal1,3, and Horst Hahn1 — 1Institute of Nanotechnology, Karlsruhe Institute of Technology, Germany — 2Donetsk Institute for Physics and Engineering, NASU, Ukraine — 3Institute of Solid State Physics RAS, Russia
Here we report our results on the behavior of interfaces in the layered metallic samples under high pressure torsion (HPT). We found the development of plastic instabilities in initially flat layers during HPT and the formation of folds and vortices.
These phenomena cannot be explained by the Kelvin-Helmholtz instability mechanism. An important condition to observe the Kelvin-Helmholtz instability is that in the flowing matter the forces of inertia are of the same order of magnitude as the internal forces due to the atomic (or molecular) interactions. In this context in metal under plastic flow a role of such internal forces play forces related to flow stress. However, it is known that at moderate strain rate deformation the forces of inertia are significantly lesser than these associated with flow stress.
Using Finite Element Modeling we show that the formation of vortices during the HPT deformation occurs when the simple shear velocity field is blocked locally within the layers, or at the interfaces. As a result, the rotation of the material takes place on macroscopic level, i.e. the formation of the vortices is observed.