Atomistic insights into the prismatic dislocation loop on Al (1 0 0) during nanoindentation investigated by molecular dynamics

Abstract

To understand the dislocation mechanism during nanoindentation on metallic materials, molecular dynamics has been widely used. It has been found that isolated prismatic dislocation loop can be formed beneath the indenter among many materials. However, there is still argument on its formation mechanism. Herein, molecular dynamics simulation has been carried on Al (1 0 0) to understand the formation mechanism of prismatic dislocation loop during nanoindentation by a rigid hemispherical diamond indenter. Based on the force-displacement curve, the generation and evolution of the crystal defects are analyzed. A new three-step mechanism for the formation of prismatic dislocation loop is proposed, and it includes three steps: (1) reactions happen between Shockley partial dislocations, and then a stair-rod forms; (2) the resultant stair-rod reacts with a Shockley partial dislocation, and then a new Shockley partial dislocation forms; (3) annihilation occurs between Shockley partial dislocations and finally a prismatic loop is released. In addition, the motion of the prismatic dislocation loop can be influenced greatly by holding the indenter at the maximum indentation depth.