Study of Processability of Cu/Ni Bilayers Using Molecular Dynamics Simulations

Nanoscratching and nanoindentation simulations are performed to study the processability of Cu/Ni bilayers with interfaces using molecular dynamics (MD) method. Single crystals Cu and Ni are served as comparisons. In the nanoscratching processes, the interfaces of Cu/Ni bilayers appear as a barrier of dislocations gliding, and lead to larger friction forces and normal forces. For single crystals and bilayers, both their friction forces and normal forces increase with the increasement of scratch velocity at 100-300 m/s. Friction coefficients under scratching processes are calculated, and they are smaller than macrosacle scratching process because of coating effects of nano-chips on the tool. The effects are analyzed by conducting both molecular dynamics simulations in nanoscale and finite element simulations (FES) in macroscale. In the indentation process, the processing properties of Cu-Ni and Ni-Cu bilayers are different from each other, and their indentation forces are both larger than their single crystals. Recovery deformation takes place during the relaxation stage. When the tool is unloading, some workpiece atoms adhere to the tool. The simulation results of the two nanoscale machining processes reveal the strengthening mechanism of interface, and show comprehensive processability of metal bilayers.