Nucleation of dynamic recrystallization at triple junctions in polycrystalline copper

The preferential nucleation of dynamic recrystallization (DRX) was investigated in copper polycrystals. DRX nucleation began to appear preferentially at triple junctions (TJs) at around 0.01 strain irrespective of the testing conditions, i.e. at only about 1/10 to 1/20 of the peak strain. The likelihood of DRX nucleation at TJs increased monotonically with strain. Furthermore, this probability also depended strongly on the strain rate, temperature and initial grain size. More than 80% of the grains nucleated at TJs were twins. The observed likelihood of DRX nucleation at TJs was closely related to the amount of grain-boundary sliding, fold formation at the TJs, the misorientation angle of the grain boundaries composing the TJ, and the angle between the tensile axis and the sliding grain boundary. The mechanisms determining the strain-rate dependence of DRX nucleation and twin formation are discussed in detail in relation to the above factors.