⟨001⟩軸方位Cu-15 at%Al合金単結晶の高温定常変形

抄録

Copper-15 at% Al alloy single crystals with the ⟨001⟩ axis were deformed in tension at 873 and 973 K. The stress-strain curve exhibits a rapid work hardening initially and then levels off after several percent strain. In this stage, the condition of steady state deformation was satisfied. In the steady-state stage, the internal and effective stress levels were determined by the stress dip test using an extrapolation technique. Dislocation substructures formed in this stage were observed by the etch pit technique. The results obtained are as follows:
(1) The axial orientation is stable during the entire period of deformation and the slip occurs on the four {111} planes at the same time.
(2) In the steady-state stage, a cellular dislocation structure was built up. The dislocation density was proportional to the square of the applied stress. The cell size was inversely proportional to the square root of the dislocation density and to the applied stress.
(3) The strain rate was proportional to the nth power of the applied stress, n being 3.8 at 873 K, or 3.6 at 973 K. These values are small in comparison with the Cu-Al alloy single crystals oriented for a single slip system. The difference in n arises from the difference of the dislocation structure between these alloys formed in the steady-state stages.
(4) The ratio of the internal stress to the applied stress was 0.65∼0.8, depending on the applied stress monotonously.
(5) The parameter m^*, the effective stress sensitivity of dislocation glide velocity, was found to be nearly unity. This result indicates that high-temperature deformation of Cu-Al alloys is controlled by the viscous motion of dislocation in spite of the high n value.