Optimization of the grain boundary character distribution of pure copper by low-strain thermomechanical processing

Abstract

Abstract Although thermomechanical processing has been widely used in grain boundary engineering, the relationship between thermomechanical parameters and grain boundary character distribution is still not well understood. In the present study, electron backscatter diffraction was used to study the grain boundary character distribution in pure copper after lowstrain thermomechanical treatments. It was found that the low-R coincidence site lattice frequency and grain size decreases in the following sequence, 10% compression > 15% compression > 5% compression, except for 700 0C. During thermomechanical treatments of copper, strain-induced grain boundary migration and grain growth may occur during annealing of 5% compressed copper, and recrystallization dominates during annealing of 15% compressed copper, while the annealing mechanism of 10% compressed copper changes from strain-induced grain boundary migration and grain growth to recrystallization when the annealing temperature exceeds 600 0C. The results indicated that during single-step low-strain thermomechanical treatments, straininduced grain boundary migration and grain growth would gradually change to recrystallization with the increase of pre-deformation level and annealing temperature. Among the three mechanisms, strain-induced grain boundary migration seems to be more effective than recrystallization and grain growth in the optimization of grain boundary character distribution, and it is suggested that this is due to the high boundary migration rate of strain-induced grain boundary migration.