Deformation Structures of Pure Titanium during Shear Deformation

Microstructure evolution of commercial pure titanium during equal channel angular pressing

“…In contrast, there is a significant frequency peak around a misorientation angle of 86 • for both points A (3 passes) and H (4 passes but off the centre axis), marked by an arrow, that indicates the presence of {1 0 1 2} twinning during the 3rd and the 4th passes of ECAP processing. In our previous work [13], we have identified {1 0 1 2} twins with width around 100 nm in the shear plane during 4th pass ECAP by using TEM and observed a similar peak to those in Fig. 8 in EBSD orientation distribution.…”

“…The accumulated misorientation increases to around 15 • over 11 μm from one side of the grain and then decreases progressively approaching the opposite grain boundary. Misorientation gradients have been examined in many coarse grains and one was described in our previous study [13]. Similar long-range misorientation gradients are found in most of the grains: the misorientation gradient across the elongation axis of the coarse grain is larger than that along the longitudinal direction.…”

“…In the last years, there has been increasing interest in investigating hard to form metals or alloys, e.g. Ti, with hexagonal close packed (HCP) structure processed by ECAP [10][11][12][13][14]. In order to obtain the finest grain size, ECAP at low temperature is a promising solution.…”

“…However, they did not study the grain refinement mechanism. In our previous work [13], the deformation structure including dislocation tangle zones (DTZ), dislocation cells (DC), twins and subgrains were investigated by electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) in the central region of the shear zone of a CP Ti sample interrupted between 3 and 4 ECAP passes. The objective of the present paper is to study the microstructure evolution of CP Ti during the 3rd and 4th pass to clarify the deformation mechanism beyond the first ECAP pass where {1 0 1 1} twinning seems to dominate.…”

“…• Grain refinement mechanism Continuous dynamic recrystallization (CDRX) occurs easily in pure titanium, due to its high stacking-fault energy [13,29]. The CDRX process is a recovery dominated process and proceeds by continuous absorption of dislocations in subgrain boundaries (LAGBs) which eventually results in the formation of new grains with HAGBs [30].…”