Molecular Dynamics Simulations of Nanoindentation of CuNi Alloy
Abstract
In this paper, molecular dynamics was used to simulate the indentation process of copper–nickel (CuNi) alloy. Its mechanical properties and behaviors were investigated focusing on factors such as indentation velocity, test temperature and crystal orientation. Generally speaking, dislocation generations and slips, stacking faults, extended dislocations and deformation twins, one or more of them come into play the dominant role during plastic deformation, which in return leads to an improved or reduced hardness of CuNi alloy. Specifically, simulations and analyses reveal the following: (1) its hardness H increases with vind increasing, but the reduced elastic modulus Er is not sensitive to vind; when it comes to test temperature T, both H and Er are reduced at elevated T; besides, the CuNi alloy along [111] owns the highest H and Er, the value of H along [001] is slightly smaller than that along [110]; (2) the dislocation density ρ varies severely in the early stage of indentation and then generally levels off when indentation depth reaches approximately 1.5nm; by and large, its hardness and dislocation density follow the classical Taylor hardening model and the hardening coefficient does depend on the three factors; (3) the plastic-zone size parameter f, when h/ac≈0.6 or equivalently h/R≈0.53 can be taken as constant roughly 4.0 except in the case of indentation along [111], in which it is about 5.7.
