Molecular Dynamics Simulation of Tensile Deformation of Iron Single Crystals Including Thermal Effect.

Abstract

Focusing on thermal distribution during deformation, ductile-brittle transition of α-iron single crystals under constant tensile stresses has been simulated by a molecular dynamics approach where the Newton equations of motion are solved utilizing the Johnson potential. A simulation where the ad-hoc velocity scaling method was used to control the deforming crystal at a low temperature showed brittle fracture starting at the notch in a plane perpendicular to the tensile direction. Another simulation where no scaling was used, where the temperature of the crystal was substantially increased during the deformation, showed plastic deformation at slip planes. From these two types of simulations, brittle-to-ductile transition of α-iron can be attributed to the temperature effect under deformation. Using a definition for local temperature at a nonequilibrium state, a substantial temperature increase was observed to occur near the crack.