MOLECULAR DYNAMICS SIMULATION OF PLASTIC BEHAVIOR OF THE Ni NANOFILM DURING SCRATCH PROCESS
纳米Ni薄膜在摩擦过程中塑性行为的分子动力学模拟

The nanoscrath process of nickel nanofilm and plastic deformation mechanisms in the nanofilm are investigated by using molecular dynamics simulation. The results reveal that the stacking faults end at the grain boundaries as well as prismatic dislocation loops, leading to that plastic deformation on the grain boundary keeps in the film rather than transmiting downward the substrate. For thinner films, stacking faults are preferred in the scratch process, which increase storage capacity of plastic deformation in the film, and further inhibit the stick–slip amplitude in the friction oscillation process. For thicker films, dislocation loops, which glide along slip plane downward to the grain boundary, dominate over the stacking faults, and finally dissipate on the grain boundaries. Since the intergrain stacking faults are inactive in thicker films, the stick–slip phenomenon is similar to that in single crystal. The evolutions of subsurface microstructures in the nanoscratch process result from the dislocation structures emitted in nanofilms with different thickness.