Twinning Behavior of a Basal Textured Commercially Pure Titanium Alloy TA2 at Ambient and Cryogenic Temperatures

Twinning greatly affects the microstructure and mechanical performance of titanium alloys. The twinning behavior of a basal textured commercially pure titanium TA2 plates rolled to 4% reduction at the ambient and cryogenic temperatures has been investigated. Microstructures of the rolled samples were investigated by optical microscope (OM) and the twinning analysis was carried out based on orientation data collected by electron back-scatter diffraction (EBSD). {112} contraction twins, {114} contraction twins and {102} extension twins have been observed. Twinning mode activity varied with rolling temperature. Twinning is considered as the dominant deformation mechanism during rolling at both temperatures for the strain condition. Larger proportion of grains activates twinning during cryorolling, and greater number and more diverse types of twins are observed; manifestly related to the suppression of dislocation slips at the cryogenic temperature. {112} contraction twins are the dominate twin type within samples rolled at both temperatures. Several {114} contraction twins are observed in the cryorolled sample while there are only a few in the sample rolled at room temperature. A few tiny {102} twins have been identified in both samples. {114} contraction twins are preferentially activated at cryogenic deformation temperature and the {102} extension twins may result in local strain accommodation.