Kocks-Mecking-Estrin type model for high-temperature creep of Zircaloy-4

Results of known detailed microstructural studies of the Zircaloy-4 at various creep stages were used to validate the conventional microstructure-based MKE approach, modeling the kinetics of the production and recombination of dislocations. The developed model is considered a tool to interpret the governing mechanisms of deformation. The strain rate in non-stationary dislocation structures was determined by the mobility of dislocations in an external stress field, lowered by the back-stress imposed dislocation structure. The rate of microstructure recovery determines the steady-state regime`s strain rate. As the root of power-law creep is still a disputable issue, microstructure recovery is analyzed in the view of conservative and non-conservative climb processes. It is shown that at least in materials where dipole instability is observed, the conservative climb may cause a change in activation energy and power-law exponent value close to the fifth power law.