Molecular dynamics simulation of temperature dependence of dislocation behavior in fcc Ni single crystal under tensile condition

Abstract

A molecular dynamics (MD) simulation of plastic deformation under a uniaxial tensile strain condition for fcc Ni single crystals is performed in order to clarify the temperature dependence of the edge dislocation behavior. Simulations are performed for the temperature range from 77 to 1200 K using Finnis-Sinclair-type potentials. An edge dislocation first forms at the surface and propagates inside of the crystal on the {111} planes in the 〈112〉 direction. The temperature dependence of the simulated Young's modulus is quite similar to the experimental results. The transverse sound velocity is estimated from the simulated elastic constants at each temperature. Below 600 K, the dislocation speed reaches up to 70% of the transverse sound velocity. The dislocation speed decreases with increasing temperature linearly above 600 K. Dislocations at elevated temperature propagate under lower stress than at room temperature. The extrapolated dislocation speed becomes zero at 1200 K. At this temperature, no dislocations are observed in the present simulation system. The temperature dependence of macroscopic deformation behavior and the possibility of the existence of supersonic dislocations are discussed.