Abstract:

The work hardening and dynamic softening behaviors of Cu-6 wt pct Ag binary alloy were studied by hot compression tests under temperature range of 700—850 ℃ at strain rates of 0.01—10 s ⁻¹ . The critical conditions for the onset of dynamic recrystallization (DRX) were determined based on the conventional strain hardening rate curves (dσ/ dε versus σ). The progress of DRX was analyzed by constructing a model of volume fraction of DRX based on flow curves. The strain rate sensitivity (SRS) and activation volume V ^∗ were calculated. The results show that the DRX almost can happen under all deformation conditions even at high Z deformations where dynamic recovery (DRV) is the main softening mechanism. The DRX fraction curves can well predict the DRX behavior. The strain has significant effects on SRS at the strain rates of 0.01 s⁻¹ and 10 s⁻¹ which are mainly due to off-equilibrium saturation of dislocation storage and annihilation while the effects of the temperature on the SRS are based on the uniformity of microstructure distribution. The formation of “forest” of dislocation is contributed to the low activation volume V ^∗ (about 168b³) which is independent of Z values at the initial deformation. The cross-slip due to dislocation piled up beyond the grain boundaries or obstacles is related to the low activation volume under the high Z deformation conditions at high strain (ε=0.6) while the fine DRX grains coarsed is the main reason for the high activation volume at low Z under the same strain conditions.

Key words: Cu-Ag alloy, Work hardening, Dynamic recrystallization, Strain