Atomic simulation of cyclic deformation in very thin wire of nickel
Kitamura Takayuki; Yashiro Kisaragi; Iehara Masato; Ohtani Ryuichi
Abstract:The mechanism of cyclic deformation is investigated by means of atomic simulation using an inter atomic potential in the embedded atom method (EAM). A very thin wire of nickel single, perfect crystal is subjected to cyclic straining. The yielding tension is brought about by a slip of partial dislocation from one surface side to the opposite one on (111) plane, which brings about a stacking fault there. When the tensile strain is continued to be applied, another partial dislocation goes through the plane and the combined slips of the dislocations bring about migration toward [101] direction on the slip plane. Although the stacking fault disappears by the passage of second dislocation, steps remain on the surface around the wire. In unloading process, the crystallographic slip are easy to take place on the stacking fault because the fault increases the potential energy of wire. Two types of slips, which dissolve the stacking fault, are observed during the unloading process. One is the reverse slip that dislocation moves back. The other is the slip of another partial dislocation on the plane toward [11 over bar 0] direction where the steps are formed on the surface though the stacking fault disappears. The latter slip, which is irreversible, forms intrusion and/or extrusion sites on the surface in cyclic straining. Key Words:atomic simulation, cyclic straining, nickel, dislocation, stacking fault, crack initiation