Four kinds of Cu-Ni alloys (90Ni-Cu, 78Ni-Cu, 40Ni-Cu, 10Ni-Cu) were crept to investigate the effect of solute atom on the creep behavior over the temperature range of 558-676K (0.4Tm) and at the stress levels from 127 to 256MPa.
Experimental condition is choosen such that creep deformation mechanism is predicted to be controlled by pipe diffusion induced climb controlled creep process.
Under the above test conditions, results shows that the static and the cyclic creep deformation are affected by thermodynamic factor and the measured activation energy for the creep deformation of alloys is found to be lower than that of lattice diffusion by the factor of 0.5
Cyclic creep accelation is observed under the stress of 197MPa at 40Ni and it can be explained that the excess vacancy generated mechanicaly under cyclic creep assist the recovery process through dislocation climb.
To explain the above results, proper creep equation is proposed by
$\varepsilon_s = K \frac{1}{b^2} (\frac{\gamma}{Eb})^3 (D_L + f_pD_p) (\sigma/E)^3 (T.F.)$
Where E is Young's modulus, b is berger's vector, $\gamma$ is stacking fault energy, D is lattice diffusion coefficient, Dp is pipe diffusion coefficient and T.F. is thermodynamic factor.
