Nano mechanical property analysis of single crystal copper using Berkovich nano indenter and molecular dynamic simulation

Abstract

Nanoindentation analysis of FCC single crystal copper with different crystal orientations under Berkovich indenter was carried out by molecular dynamics simulation. The influence of crystal orientation on load distribution under Berkovich indenter was studied and compared with the experiment. Simultaneously, by establishing the relationship between the load–displacement curve and the instantaneous defect structure, the defect formation and slip processes under different crystal orientations were analyzed. Finally, the dislocation density of different orientations was calculated. Meantime, the relationship between the dislocation density and the hardness was explored. The results show that the 〈100〉 orientation shows a slightly different anisotropy difference, and the load value is lower than the 〈110〉 and 〈111〉 orientations. The 〈111〉 load value is slightly greater than 〈110〉 and the hardness values also show the same trend as the load value. The launch time of the initial dislocation loop of 〈100〉 orientation is earlier than 〈110〉, 〈111〉. The crystallographic orientation has a great influence on the change of dislocation morphology during the indentation process. With different orientations, the main plastic deformation is incomplete dislocation nucleation. Under different orientations, different forms of dislocation proliferation, such as quadruple, double and triple symmetry, and different stacking slip directions activated during indentation are observed. The 〈110〉 orientation has a relatively small dislocation density value, the dislocation density ρ0.5 is proportional to the hardness, and the coefficient values are different with different orientations.