Experimental Investigations On Initial Deformation Behaviors Of Single Crystal Copper In Nanoindentation

Nano-electro-mechanical systems (NEMS) and micro-electro-mechanical systems (MEMS), which are characterized for the micro profile scale and minimal operating sizes, have drawn much attention form people. The specimen which has a dimensional size smaller than 100μm will bring difficulties for the conventional compression test and tension test. As tiny indentation is left on the surface of the material, nanoindentation tests become a primary working method for mechanical properties testing at micro and nano scale. However, there is a lack of systematic study of nanoindentation mechanism, and many of them were concerned on simulation. The experimental investigations of materials mechanical behaviors in nanoindentation are limited. Therefore, experimental investigations of deformation behaviors of materials at micro and nano scale are urgently required.In order to study the deformation behaviors of single crystal FCC metals at micro and nano scale, a series of nanoindentation test were employed to investigate the initial plastic deformation behaviors of single crystal copper. The effects of surface features and crystal defects were also investigated.Nanoindentation test are employed on (100) plan and (110) plan of single crystal copper. Differences of the experimental data show that (100) plan experiences more elastic deformation in nanoindentation tests. The reasons and effects of pile up around indentation are analyzed, indicating that the occurrence of pile up phenomenon will over evaluate the tested hardness value and modulus value.In order to investigate the effects of surface features on initial plastic deformation of single crystal copper, the specimens were annealed in circles and surface steps were obtained. Comparisons of load-displacement curves above and under surface steps showing that the existence of surface steps have no effects on the mechanism of initial plastic deformation of single crystal copper and the first pop-in phenomenon of the load-displacement curve.Dislocation patterns around indentation points on (110) plan were observed via TEM. The stacking fault, partial dislocation, and dislocation loops were...