Shear strain accommodation during severe plastic deformation of titanium using equal channel angular pressing

In the present study, microstructural changes in commercially pure titanium during equal channel angular (ECA) pressing were examined. Elongated grains inclined by 25° to the longitudinal direction were developed and these grains contained high-density twins. TEM analysis of the twins revealed that their twin plane is {101̄1} and the twins are accompanied with dislocations on non-basal planes. These results suggest that the severe plastic deformation imposed on titanium via ECA pressing is accommodated mainly by the {101̄1} twinning, rather than dislocation slips commonly observed in pressing of other metals such as aluminum and steel. The twinning modes that might accommodate the severe strain were proposed based on the dislocation slip systems observed during the pressing.