reports on the dynamic misorientation change absorbed by the grain boundaries themselves during one-pass equal-channel angular pressing (ECAP), the effect of grain boundary structure on the misorientation change during ECAP was examined as the next step. Two bicrystals with a 3{111} grain boundary and a random one were subjected to ECAP for one pass, and compared. Both the bicrystals were designed to have a similar slip pattern where slip activity was concentrated on one slip plane. Direct evidence of misorientation changes absorbed by grain boundary themselves was obtained again, and its marked dependency on grain boundary structure became evident. Namely, in 3 grain boundary, misorientation was partially carried by the grain interior in its vicinity, which stems from the dislocation accumulation. On the other hand, in the random grain boundary, most of the misorientation was carried by the boundary itself. These differences are discussed in terms of the capability as a sink of lattice dislocations during severe plastic deformation.

Grain boundaries can change their misorientation by absorbing lattice dislocations at relatively high temperature under moderate straining. The same phenomenon is believed to occur during severe plastic deformation down to room temperature leaving grain boundaries in the nonequilibrium state. Direct evidence of misorientation change of the grain boundary during severe plastic deformation was obtained in copper bicrystals subjected to equal-channel angular pressing (ECAP) for one pass. Marked dependence of misorientaion change on the initial orientation was revealed, and is associated with the unique slip patterns of ECAP, where the shear deformation is restricted to the narrow zone parallel to the intersecting plane of the two channels. The degree of change can be related to slip geometry in terms of grain boundary plane orientation.