Creep of a Cu-2·5 at. pct. Al alloy at high temperatures

The creep of a Cu-2·5 at.pct. Al alloy has been investigated by the isothermal tests technique. Two dislocation mechanisms operate in parallel in the investigated temperature region. In the region of lower minimum creep rates ( <3×10^–5 sec^–1) — region 1 — the activation energy of creep is close to the expected value of the activation enthalpy of the lattice self-diffusion of copper in the alloy. The stress dependence of the minimum creep rate can be described by a power function of the ⁿ type, where n=n₁=5·8. The results for region 1 can be satisfactorily correlated with the model of nonconservative motion of jogs on screw dislocations dependent on lattice self-diffusion. If a power function of the ^m type is used to describe the minimum creep rate dependence on the stacking fault energy, thenm is equal to –0.66.In the region of higher minimum creep rates — region 2 — the apparent activation energy is higher than the expected value of the activation enthalpy of lattice self-diffusion of any component in the investigated alloy. The dislocation mechanism dominating in region 2 has not been identified.The influence of stacking fault energy on the minimum creep rate in region 2 is weak or even zero.