Power Law Breakdown in the Creep in Single-Phase Metals

Abstract

New analysis provides insight into the basis of power-law breakdown (PLB) in the steady-state creep of metals and alloys. A variety of theories has been presented in the past but this new examination suggests that there is evidence that a dramatic supersaturation of vacancies leading to very high diffusion rates and enhanced dislocation climb is associated with the rate-controlling process for creep in PLB. The effect of vacancy supersaturation may be enhanced by dislocation short circuit diffusion paths at lower temperatures due to the dramatic increase in dislocation density.

The transition from the power-law to the power-law breakdown regimes in thermal creep of Zr1%Nb cladding alloys

“…Nevertheless, as mentioned earlier, a view on the rate controlling creep mechanism(s) in the PLB regime has not yet been successfully answered. A variety of theories has been reported over the past five decades but has not been sufficiently verified [44][45][46][47][48][49][50][51]. Very recently, Kassner and Ermagan [50] published a new analysis that provides contemporary insight into frequently considered mechanisms of power-law breakdown in the creep of metals.…”

“…A variety of theories has been reported over the past five decades but has not been sufficiently verified [44][45][46][47][48][49][50][51]. Very recently, Kassner and Ermagan [50] published a new analysis that provides contemporary insight into frequently considered mechanisms of power-law breakdown in the creep of metals. Kassner and Ermagan [50] anticipated that a dramatic supersaturation of vacancies leading to very high diffusion rates and enhanced dislocation climb is associated with the rate--controlling process for creep in the PLB regime.…”

“…Very recently, Kassner and Ermagan [50] published a new analysis that provides contemporary insight into frequently considered mechanisms of power-law breakdown in the creep of metals. Kassner and Ermagan [50] anticipated that a dramatic supersaturation of vacancies leading to very high diffusion rates and enhanced dislocation climb is associated with the rate--controlling process for creep in the PLB regime. It should be noted that in an earlier work by Sherby and Burke [45], an idea was already propounded that excess lattice vacancies by dislocation intersection processes in creep at high stresses will enhance dislocation climb and, therefore, make creep easier.…”

“…However, a complete understanding of the creep deformation and fracture mechanisms operating in a Zr1%Nb alloy is still missing [3][4][5]. Despite the important basic understanding of creep behaviour in zirconium alloys, there appears to be insufficient creep data in the literature describing the thermal creep in the transition between the power-law (PL) creep regime at moderate applied stresses controlled by dislocation climb and the power-law breakdown (PLB) regime at high stresses [2,6,7]. In fact, the *Corresponding author: e-mail address: sklen@ipm.cz mechanism of creep deformation in the PLB is poorly understood due to a limited number of studies carried out in this regime.…”

New Developments in Understanding Harper–Dorn, Five-Power Law Creep and Power-Law Breakdown

“…There have been various explanations for PLB [50][51][52][53][54]: (1) It has been proposed that there is a change in the rate-controlling mechanism of steady-state plastic flow from dislocation climb-control in 5-PL to glide-control in PLB. However, this proposition is sometimes based on the presence of internal stress which does not appear to be reasonable as the long-range internal stresses (usually suggested to give rise to high local stresses at dislocation heterogeneities) appears to be low in both the PL and PLB regimes [17].…”