Recovery of a creep-deformed Type 316 stainless steel

Self-consistent modelling of cyclic loading and relaxation in austenitic 316H stainless steel

“…During cyclic loading the dislocation structure is refined due to the reduction in spacing between the obstacles to dislocation motion, resulting from the intersection between dislocation link segments during slip [2], as part of the continuous interaction between self/latent hardening and dynamic recovery. Once the dislocation obstacle network is refined, a balance between hardening and thermal (static) recovery at high temperature during creep loading is reached faster since the rate of static recovery by dislocation climb processes would be greater for the higher dislocation densities, as suggested by Morris and Harris [28]. The reduction of creep rate during primary creep is believed to be as a result of the competition between hardening and static recovery until a dynamic balance between the two processes is reached, which is taken as the start of the secondary creep stage, where the creep rate usually reaches a minimum [1].…”

“…Phenomenologically, the creep part of the stress relaxation at longer times is often related to creep recovery at high temperature with the rate-controlling mechanism being dislocation climb [27,28]. It is important to note, however, that in Type 316 stainless steel the creep-controlling mechanisms in the temperature range between 500-650°C can change significantly [21,22,29,30].…”

The effect of cyclic-loading generated intergranular strains on the creep deformation of a polycrystalline material

“…This effect has been reported by Joseph et al [28] for type 316H stainless steel at 550 °C. Cyclic loading is believed to reduce the spacing between dislocations and obstacles which makes static recovery by dislocation climb processes faster [29]. This accelerates the balance between hardening and recovery [30] and thereby promotes early secondary creep behaviour.…”

Creep-fatigue interactions in type 316H under typical high-temperature power plant operating conditions

“…Once the dislocation obstacle network is refined, the balance between hardening and thermal recovery during creep loading is achieved quicker. As a result, lower amounts of creep strain are accumulated during primary creep, since the rate of static recovery by dislocation climb would be greater for the higher dislocation densities, as suggested by Morris and Harris [30]. In a similar fashion, the minimum creep rate during the dwell in fully-hardened material is decreased, which stems from the higher dislocation obstacle densities in cyclically-deformed samples.…”