Faceted interfacial structure of {101¯1} twins in Ti formed during equal channel angular pressing

The boundary structure of {101¯1} deformation twins formed in commercially pure titanium during an initial pass of equal channel angular pressing processing has been studied by transmission electron microscopy (TEM) and high-resolution TEM. A new twinning mode with a twinning dislocation of b3/3 has been identified using a dichromatic diagram method. The new mode of the {101¯1} twin has substantially higher interface energy and accommodates more shear strain during deformation than the conventional b4 twinning mode. The deviation angle between the habit trace of the twin boundary and the theoretical twinning plane, K1, is dependent upon the density of twin dislocations.