Stress dependence of high-temperature creep in Fe−Mo and Fe−Co alloys

Abstract

The stress dependence of high-temperature creep and the alloying effects on it were investigated both in the ferromagnetic and the paramagnetic temperature regions of alpha iron and Fe−Mo and Fe−Co alloys. The steady-state creep rate,$\dot \varepsilon _s$, of alpha iron was found to obey a power law relationship,$\dot \varepsilon _s \propto \sigma ^n$ (n: constant) in the temperature range above 0.5T _m (T _m : the melting temperature). The stress exponent,n, was 4.6 at all the temperatures examined. By addition of molybdenumn decreased to 3, while it remained unchanged by addition of cobalt. It seems that the change inn due to alloying is mainly attributed to the change in activation area for creep,A ^*, which results in the change in stress dependence of dislocation velocity. The magnetic transformation was found not to influence the stress dependence of$\dot \varepsilon _s$.