Atomic-Scale Study on the Dislocation Evolution Mechanism of Al/Cu-Layered Materials Under Nanoindentation

Al/Cu-layered metal materials, a kind of material with a highly ordered structure and excellent comprehensive performance, are widely used in the fields of automobile, aerospace and shipbuilding. The molecular dynamics method was adopted to simulate the mechanical behavior and dislocation evolution mechanism of Al/Cu-layered materials at different indentation velocities; the results indicating the uniquely periodic dislocation network formed during deformation at the interface can prevent further dislocation slip and relieve stress concentration, leading to the improvement of the strength and hardness. The interface dislocation can be activated when the indentation depth is sufficient, along with the location and slip system, depending on the symmetry of the crystal structure and the Schmidt factor. Moreover, the plastic deformation begins with the nucleation and movement of Shockley partial dislocations and is dominated by the dislocation slip. With the increase of indentation velocity, the movement and reaction of dislocations are promoted, which have an emergence of immobile dislocations, complex dislocation loops, many dislocation tangles and limited dislocation cross-slip, greatly accelerating the work hardening and delaying the deformation. Particularly, there are two main steps in the formation of independent prismatic dislocation loops. First, multiple “u”-type dislocation loops nucleate and then slip. Second, the screw dislocation fragments of the shear dislocation loop cross-slip on the intersecting [Formula: see text] slip plane. The research results open a window in manufacturing nanoprecision devices, analyzing the service performance and carrying out reliability evaluation.