Vortices in Noncompact Blanks During Twist Extrusion

Abstract

The causes and consequences of the formation of multifractal vortices during severe plastic deformation of powder and porous bodies by twist extrusion are analyzed. It is demonstrated that the developed pore space in noncompact blanks leads to the formation of self-similar vortices at different scales. It is established that the multifractal vortices occurring during simple shear in twist extrusion, are responsible for the differences in the mechanisms of hardening of compact and noncompact materials. Being significantly increased (in comparison with the concentric streamlines during deformation of compacted materials), the integral deformation path intensifies the accommodation of particles of a mixture of powder components. In addition, the vortices cause intensive mixing and mass transfer at both micro and macro scales. The intensive mass transfer leads to chemical and structural homogenization and elimination of porosity.