7. Temperature and Thickness Dependent Mechanical Properties of Ti/Ni Multilayer Thin Films

Strong temperature and thickness dependent mechanical properties of Ti/Ni multilayer thin films have been observed with layer thickness from 200 nm to 6 nm and annealing temperature from room temperature to 500 °C. The as-deposited case follows the traditional trend of dislocation mediated-strengthening to grain boundary mediated-softening with decreasing layer thickness. Initial thermal strengthening of multilayers is achieved by annealing induced grain boundary relaxation. This strengthening is found to increase with decreasing layer thickness and increasing annealing temperature. Further strengthening could be achieved due to solid solution of diffused atoms and Ti-Ni intermetallic precipitates for multilayers with thin layer, while obvious softening has been observed for multilayers with thick layer due to recrystallization and grain growth.