Temperature dependence in nanoindentation of a metal substrate by a diamondlike tip

In this investigation, we simulated the nanoindentation of a copper substrate by a diamondlike tip, using molecular dynamics method. A series of simulations according to distinct system temperatures were performed to analyze the temperature dependences of some important physical quantities occurring in the indentation. We found that the maximal normal forces on the tip atoms, both the repulsive and the attractive, the elastic modulus of the indentation system and the network done by the tip during the indentation cycle all decrease with increasing system temperature. By these dependences, we then identified the critical temperature for the transition of plastic flow mechanism in the substrate. The evolution of the crystalline structure in the substrate was analyzed by examining the variation of the structure factor, which measures the perfection of the crystalline structure, during the indentation cycle. An important physical quantity is the difference between the equilibrium absolute values of structure factor before and after the indentation, which can be used to measure the permanent deformation in the substrate produced by the indentation. We found that the difference increases with increasing temperature if the system temperature is below the critical temperature.