3.4 grain boundaries distribution
The grain boundaries distribution
maps of X90 bend zone analyzed by EBSD are shown in Fig. 9.
In the grain boundaries distribution
maps, the black lines represent the high angle grain boundaries (HAGBs)
that greater than 15°, and the red lines correspond to low angle grain
boundaries (LAGBs) were characterized as boundaries with misorientation
of 2° ~ 15°. In the crystallographic theory, these two
types of grain boundaries are usually used to represent the main grain
boundaries. HAGBs are the grain boundaries of PF and LB. Moreover, some
bainite packet boundaries can be regarded as Σ3 (<
111>/ 60°) boundaries according to the typical
Kurdjumov-Sachs (K-S) orientation relationship [29, 30]. Some
sub-grain boundaries inside the PF are regarded as LAGBs.