Creep in zirconium at low stresses and temperatures from 748 to 973 K

The results of an investigation of creep in Zr-ALPHA at stresses ranging at temperatures ranging from 748 to 973 K and with linear intercept grain sizes less than 120 microm are presented. It is shown that the steady state creep rate is inversely proportional to the third power of intercept grain size, increases with the stress linearly and is grain boundary diffusion controlled. For steady state creep a threshold stress is characteristic. The results are correlated with the model of non-uniform diffusional flow due to Ashby and Verrall. The measured threshold stress is accounted for on the assumption that it represents the stress opposing the motion of grain boundary dislocations. From the results of the present work together with those of previous work on power law creep and Harper-Dorn creep in Zr-ALPHA creep mechanism maps were constructed. (orig./WE)