Whirls Occurring in Noncompact Billets during Twist Extrusion

D.V.Pavlenko,
 
Ya.E.Beigelzimer
 

Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2015, #09/10
http://www.materials.kiev.ua/article/1993

Abstract

Causes and consequences of formation of multifractal vortices during an intensive plastic deformation of powder and porous bodies by twist extrusion are analyzed. It is demonstrated that the developed pore space of un-compacted blanks leads to the formation of self-alike vortices at different scale levels. It is established that, during simple shear in twist extruding, the multifractal vortices specify differences in the mechanisms of hardening compacted and un-compacted materials. Being significantly increased (in comparison with the concentric threads of current during deformation of compacted material), the integral deformation way intensifies the accommodating of particles of the powder component mixture. In addition, the vortices cause an intensive mixing and mass transfer at both micro and macro levels. The intensive mass transfer leads to chemical and structural homogenization and elimination of porosity.


DENSIFICATION, FRACTAL, HOMOGENIZATION, MASS TRANSPORT, POWDER, TWIST-EXTRUSION, UN-COMPACTED MATERIAL, VORTEX