Twinning behavior in the Ti-5Â at.% Al single crystals during cyclic loading along [0Â 0Â 0Â 1]

Cyclic deformation behavior of Ti-5 at.% Al single crystals subjected to pull-push cyclic load along [0 0 0 1] crystallographic orientation was studied. A higher cyclic stress response was displayed in the Ti-5Al single crystal oriented for [0 0 0 1] than that oriented for single prism slip. Optical microscopy and transmission electron microscopy examinations show that twinning is a dominant plastic deformation mode in the single crystals during cycling. Trace analysis of prepolished surfaces was used to identify the twin systems primarily responsible for deformation. The major twin type observed was {1 0 1¯ 2}, {1 1 2¯ 2}, {1 0 1¯ 1} and {1 1 2¯ 1}. 〈c + a〉 slip was observed in the neighboring region of twins in the fatigued specimens. The activation of multiple twinning systems contributed to the higher cyclic saturation stress in Ti-5Al single crystals oriented for [0 0 0 1].