Abstract
To clarify the effects of vacuum on the room-temperature time-dependent deformation of Ti nanocolumns, we conducted monotonically-increasing-loading experiments with different loading rates and creep experiments using micro-specimens in laboratory air and vacuum environments. In the monotonically-increasing-loading experiments, critical apparent shear stress, defined as the critical force divided by specimen area, in air environment was larger than that in vacuum environment. The result indicated that an environmental effect existed and significantly influenced the strength. In air environment, the loading curves (apparent shear stress vs. displacement curves) were almost similar at the large loading rates 50 μN/s and 100 μN/s, whereas the fracture displacement at the small loading rate 5 μN/s was five times as high as those at the large loading rates. On the other hand, in vacuum environment, the loading curve at 5 μN/s was almost similar to those at the higher rates 50 μN/s and 100 μN/s. In the creep experiments, the Ti nanocolumns showed time-dependent deformation in both air and vacuum environments. The steady state creep rate in air environment was much higher than that in vacuum environment. These results suggested that the time-dependent deformation in the nanocolumns was significantly accelerated by air or moisture environment.
