Author Description

This dissertation, "The Nanoindentation Size Effects of Creep" by Han, Li,, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled: The Nanoindentation Size Effects of Creep Submitted by LI, Han for the degree of Master of Philosophy at The University of Hong Kong in December, 2004 Nanoindentation provides convenient and localized measurements of the mechanical properties of materials, and is an especially useful technique for the study of thin films and materials of small volumes. Previous investigations showed that the submicron contacts with the rigid indenting punch could yield creep at an enormous speed at low homologous temperatures, where the same material in bulk condition would normally not exhibit any creep. The influence of this time dependent deformation on the calculation of material properties has been investigated, and compensation methods have been proposed, but the fundamental mechanisms leading to such a high creep rate remain unknown. It would also be interesting to establish if creep behavior and its mechanisms change as the indent size diminishes towards incipient plasticity, and if so, how. The aim of this study is therefore to investigate the characteristics and mechanisms of the nanoindentation creep in different materials over a wide range of indent sizes (from several nm to above one micron). A depth-sensing, constant load creep test was used to measure the stress exponent, chosen to quantify indentation creep behavior, at different indentation sizes on both Ni Al (111) single crystal, polycrystalline Al, amorphous fused quartz and nanocrystalline