Investigation of nanoindentation applications and effects on single crystal copper, silicon and Al-Si, Cu-Nii alloy materials

Nowadays, rapid developments in technology have made it possible to design and manufacture devices at micro and nano scales. Therefore, characterization of materials at micro and nano levels is of great importance. In this study, nanoindentation tests and molecular dynamics (MD) simulations were carried out in order to investigate the mechanical properties such as hardness, elastic modulus and surface deformation of Cu-Ni and Al-Si alloys and Cu[100] and Si[100] single crystals produced by casting method. Nanoindentation experiments were applied with nano test devices under 5000 µN and 10000 µN loads using Berkovich type tips. Indentation speed was determined as 500 m/s in MD simulations. Nanoindentation tests for Cu-Ni alloys obtained by casting method revealed that the elastic modulus varied between 101.89 GPa and 139.27 GPa. On the other hand, it was observed that these values were between 126.30 GPa and 186.34 GPa in MD simulations. The deepest indentation mark was recorded in single crystal Cu[100] metal, while the shallowest indentation was recorded in Cu-%10Ni alloy. In Al-Si alloys, it was determined that indentation displacements increased, applied forces decreased and dislocation density decreased with increasing silicon content. In addition, it was calculated that Cu-%10Ni alloy with larger grain sizes had a hardness value of 2.40 GPa, whereas this value increased to 3.90 GPa in Cu-%20Ni alloy with smaller grain sizes. The heterogeneous distribution of silicon in Al-Si alloys and the presence of elements such as Mg, Fe and Ag affected the pop-in and pop-out behaviors and caused differences in mechanical properties. However, no permanent dislocation formation was observed in Al-%20Si alloy. The experimental findings and MD simulation results were found to be consistent with each other; it was confirmed that MD simulations are applicable and reliable in analyzing real-time atomic scale deformations. In this context, it was concluded that MD simulations are a fast and low-cost method for determining mechanical properties such as elastic modulus and hardness in metal alloys.