Effect of grain boundaries on dynamic recrystallization behaviour of copper isoaxial bicrystals with 〈001〉 tilt boundaries

Dynamic recrystallization behaviour of copper isoaxial bicrystals with various 〈001〉 tilt boundaries was investigated at 1023 and 1073 K at an initial strain rate of 3.33×10⁻⁴sec⁻¹, with special attention paid to the effect of grain boundaries on the recrystallization stress (strain) and the substructure developed during deformation. The grain boundaries in the bicrystals have almost no effect on the stress-strain curves. Flow stress was found to fall abruptly and significantly during deformation, being similar to the flow stress in the single crystals. The stress σ_R (ɛ_R), just before the stress fall indicates the stress (strain) at which dynamic recrystallization occurs. The growth of recrystallized grains is markedly fast in these bicrystals, suggesting that dynamic recrystallization is controlled by a nucleation process. The value of σ_R in bicrystals with a tilt boundary of 9°, θ9 bicrystals, is almost equal to that in single crystals, but is larger than σ_R in θ23, θ36 and θ43 bicrystals. These results indicate that the θ9 boundary has no effect on the dynamic recrystallization of bicrystals, whereas grain boundaries with tilt angles above 23° accelerate the dynamic recrystallization of these bicrystals. The θ-dependence of σ_R or ɛ_R is discussed in connection with the stress concentration near the grain boundary.