Plastic deformation and fatigue properties of ternary CoTi based alloys containing Al at room and high temperatures

Mechanical and fatigue properties of ternary CoTi based single crystals containing 2% and 5% Al was investigated. It was shown that in these two alloys the addition of Al improve the strength of CoTi at all tested temperatures, but by increasing Al content the peak temperature shifted to lower temperature and the effect of anomalous strengthening was weakened. The number of cycles to failure in fatigue test for CoTi (2 at.% Al) single crystals showed a minimum, at high temperatures. This phenomenon seems to be due to the activation of new slip systems. Also by increasing Al, the fatigue limit at constant temperature can be changed. It was shown that Al addition is not effective in improving fatigue life at low temperatures but it can improve it at high temperatures.

► Addition of Al is effective in improving strength of CoTi at all tested temperatures.
► Al addition is not effective in improving fatigue life at low temperatures.
► Al addition improves fatigue life at high temperatures.