Nanoscale physics

Simulation of grain refinement by KoBo deformation
using a Cellular Automata model
Yu.O. Lyashenko,  A.R. Honda 
Physics Department, Cherkasy National University, Shevchenko, 81, Cherkasy, Ukraine.
E-mail: urico@ukr.net
A production of nano-grained metals by Severe Plastic Deformation (SPD) is a science and technology trend. Korbel and Bochniak suggested their own method (KoBo) for metals and alloys extrusion [1-2].
A model of KoBo SPD [3] simulation is developed based on the inverse dependence of the material's viscosity on the concentration of point defects (the higher the concentration, the less the viscosity). The interrelation between the defects concentration and deformation is used for the description of defects' diffusive redistribution. In this case, the width of of KoBo SPD [3] simulation and increased defect concentration is proportional to the surface velocity of the deformation.
In this investigation the new model that couples principles of dynamical recrystallization (DRX) with the cellular automata (CA) method [4-5] has been developed to simulate the microstructural evolution and the plastic flow during KoBo SPD. The effects of the thermomechanical parameters values (temperature, pressure) on the DRX kinetics and grain size redistribution were investigated.

1.	Bochniak W., Korbel A. Plastic flow of aluminium extruded under complex conditions // Mater. Sci. Technol.-2000.-16.-P. 664. 
2.	Gusak A., Danielewski M., Korbel A., Bochniak W., Storozhuk N. Elementary model of severe plastic deformation by KoBo process // J. Appl. Phys.-2014.-115.-P. 034905-1.
3.	Gusak A. M., Gonda A. R. Severe plastic deformation by Kobo method – estimations and model // Cherkasy University Bulletin: Phys. and Math. Sci.-2017.-1.-P. 12-21. http://phys-ejournal.cdu.edu.ua/article/view/2328/2523
4.	Ding R., Guo Z. X. Coupled quantitative simulation of Microstructural evolution and plastic flow during dynamic recrystallization Acta mater.-2001.-49.-P. 3163-3175.
5.	Chen F., Cui Z., Liu J., Chen W., Chen S. Mesoscale simulation of the high-temperature austenitizing and dynamic recrystallization by coupling a cellular automaton with a topology deformation technique // Materials Science and Engineering.-2010.-A 527.-P. 5539–5549.