High Temperature Deformation of ⟨001⟩ Single Crystals in Cu–Al₂O₃ Alloy

抄録

For the purpose of making clear the mechanism of high temperature deformation of dispersion strengthened alloys, the deformation behavior of Cu–Al₂O₃ alloy single crystals of ⟨001⟩ orientation has been studied with particular attention paid to the effect of the particle distribution, i.e., the particle diameter, d, and spacing, λ. These alloys were prepared by the internal oxidation technique. The volume fraction of Al₂O₃ in the alloys was between 0.2 and 0.8%, and d and λ were in the range of 31–64 nm and 485–815 nm, respectively. The crystals were tested in tension at temperatures between 823 and 923 K and in the initial strain rate range from 10⁻⁵ to 10⁻³ s⁻¹. The main results are summarized as follows: (1) The steady-state deformation appears after small amounts of deformation. The specimen axis hardly rotates during tensile deformation. These facts are ascribed to the operation of multiple slip from the beginning of deformation. (2) The strain rate in the steady-state deformation is represented as a power of stress normalized by the Young’s modulus. Values of the stress exponent and the activation energy for high temperature deformation are 7–9 and about 196 kJ·mol⁻¹, respectively. The latter is close to that for self-diffusion in copper. The flow stress mainly consists of the internal stress. These results suggest that the high temperature deformation of Cu–Al₂O₃ alloys is controlled by a recovery process. (3) The deformation behavior of these alloys depends on the particle distribution rather than on the volume fraction of the oxide particles. The strain rate at a given stress increases with a decrease in d and an increase in λ. (4) The stress and particle distribution dependences of the strain rate in the steady-state deformation of Cu–Al₂O₃ alloys have been discussed on the basis of creep models so far proposed for dispersion strengthened alloys. The local climb model seems to be adequate to the creep of these alloys.