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 ( {Mathematical expression}<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 σn 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 γm type is used to describe the minimum creep rate dependence on the stacking fault energy γ, then m 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. © 1969 Czechoslovak Academy of Sciences.