Microstructure Evolution in Nano-sized Wiredrawing Process:

Abstract

By using molecular dynamics (MD) simulation, the mechanism of nanometer-sized wiredrawing is studied. The possibility of nano-sized plastic working process and predictive microstructures are investigated. As a drawn material, pure iron (α-Fe) and magnesium (Mg) single crystals are compared. The MD models are constructed by utilizing many-body-type (FS or EAM) interatomic potentials with adequate modification for lubrication between wire and die. Dislocation slip is a principal mechanism of plastic deformation in the case of α-Fe in any drawing direction of single crystal. Besides, dislocation densities increases with increase of the wire diameter, where nucleation, annihilation and mutual behavior of dislocations are observed in detail. On the other hand, in Mg single crystal, mechanism of plastic deformation depends strongly on crystal orientation as to drawing direction. Twinning and twin boundaries can be identified by detecting a network of interface dislocations. When the c-axis of hcp lattice is inclined by 45 degrees from the drawing direction, dislocations on basal plane occur, but no twin, and therefore the minimum dislocation density is obtained.