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0978-GG05-09

Simulation of Dislocation Relaxation in FCC Metals Yoshiaki Kogure, Kei Sakieda, Toshio Kosugi, and Tadatoshi Nozaki Teikyo University of Science & Technology, 2525 Yatsusawa, Uenohara, 409-0193, Japan

ABSTRACT Dynamical properties of edge dislocation in copper crystals are investigated by means of molecular dynamics simulation. The embedded atom method potential is used in the simulation. Configuration and motion of dislocations in a slip plane are graphically demonstrated in 3dimentional model. Change of mean potential energy during the dislocation motion is also investigated. INTRODUCTION . The mechanical relaxation due to dislocation has been observed in copper, aluminum and other metals by means of internal friction measurements. Broad relaxation peaks observed at temperatures between 100 K and 200 K in the deformed samples are called Bordoni peak. If these relaxation peaks are analyzed based on the double kink formation mechanism, a larger value of Peierls stress, 10-3µ, is derived, where µ is the shear modulus [1]. One of the present authors Kosugi discovered a new relaxation peak at 11 K in zone refined aluminum samples, and derived Peierls stress was orders of 10-5µ, which is reasonable size as expected from the plastic deformation experiments[2] Such a low temperature peak is not observed in impure samples and in other metals. On the other hand, we have performed a molecular dynamics computer simulation of dislocation motion in 2-dimentional model. In the simulation, the total kinetic energy is found to make a bump in the time variation, when the dislocation surmount a Peierls potential hill. The Peierls stress is estimated to be the order of 10-5µ from the size of the bump[3]. The purpose of the present study is to develop a 3-dimentional model for the simulation of dislocation in copper, and investigate the structure and motion of dislocations. A newly developed embedded atom method potential [4] was used in the present simulation. The potential function has successfully applied on the simulation of the dynamics of crystal defects and nanoparticles [5-7] METHOD OF SIMULATION Molecular dynamics simulation has been performed by using an EAM potential. Potential functions are developed by the present authors. The potential energy for i -th atom is expressed as Ei = F (ρi) + (1/2) Σ φ (rij)

(1)

where F(ρi) is the embedding energy for i-th atom, and ρ i is the electron density function, which is a sum of the density of the neighbor atoms labeled by j. These are expressed as F (ρ i) = D ρ i ln ρ i

ρ i = Σ f (rij)

(2-a) (2-b)

and φ (rij) is the two body interaction between atom i and j. The functional forms of φ (rij) and f (rij) are

φ (r) = A (rc1 – r)2 exp(-c1r)

(3)

f ( r ) = B (rc2 – r)2 exp(-c2r)

(4)

where rc1 = 1.6 r 0 and rc2 = 1.9 r 0 are the truncation distance of the potential, and r0 is the nearest neighbor distance. The Potential parameters for Cu are determined to reproduce the material properties such as the cohesive energy, the elastic constants, and vacancy formation ene