Analysis of Plastic Deformation in Metal-Ceramic Nanolayers During Cyclic Indentation

The indentation behavior of metal/ceramic nanolayers is studied, with attention devoted to cyclic response under fixed maximum and minimum indentation loads. The primary objective is to examine the evolving plastic deformation in the ductile metal constrained by the hard ceramic layers. The model consists of alternating aluminum (Al) and silicon carbide (SiC) thin films on a silicon substrate, with the Al/SiC layered structure being indented by a diamond indenter. The rate-dependent viscoplastic response of Al is taken into account in the numerical model. It is shown that plastic deformation in the ductile Al layers continues to occur during the unloading phase of the first cycle, as well as during subsequent reload/unload processes. The cyclic plasticity results in an open load-displacement loop, and the indenter continues to move deeper with each cycle. For the control model of a homogeneous Al film, there is no hysteresis loop and the transient behavior soon approaches stabilization, showing repetitive elastic loading/unloading. The modeling results are also compared with cyclic nanoindentation experiments conducted on the same metal-ceramic multilayer system and control specimen.