Online

Pringle, Malcolm Ryan

Mechanical Engineering

2021

M.S.

Among all metals, silver has the highest electrical conductivity but also is one of the softest materials under mechanical deformation. Therefore, developing means and methods for strengthening silver without reducing conductivity is critically important for its use as a conductive electrode material in various engineering applications such as solar cells and touchscreen displays. This thesis presents a molecular-dynamics simulation study of strengthening mechanisms by intercalating nanocrystalline silver films with amorphous nickel layers, characterizing the structure of nanolayered material prototypes obtained by sputtering deposition technique. The objectives of the thesis are three-fold: To study the effects of Ni layer thickness and Ag film grain size on flow stress under compression, to simulate the nanoindentation hardness behavior of Ag-Ni nanolayers, and to elucidate the underlying strengthening mechanisms at atomic scale. It is found that the addition of Ni nanolayers plays a significant strengthening role as the layer thickness increases. However, the Hall-Petch strengthening breakdown observed in the pure nanocrystalline Ag model at an average grain size between 13 and 15 nm, is not observed in the models with the Ni layer. Furthermore, a discovery of dynamic recrystallization was made, that as the strain on the material grew, the Ni nanolayer became less amorphous. Nanoindentation simulations indicate that the proximity of a Ni layer does not change the hardness, and that slip transmission is not a strengthening mechanism in the material. The atomic structure of the deformed models, as a function of applied strain, is analyzed to interpret these observations.