Dislocation-mediated creep process in nanocrystalline Cu

Abstract

Nanocrystalline Cu with average grain sizes ranging from ∼ 24.4 to 131.3 nm were prepared by the electric brushplating technique. Nanoindentation tests were performed within a wide strain rate range, and the creep process of nanocrystalline Cu during the holding period and its relationship to dislocation and twin structures were examined. It was demonstrated that creep strain and creep strain rate are considerably significant for smaller grain sizes and higher loading strain rates, and are far higher than those predicted by the models of Cobble creep and grain boundary sliding. The analysis based on the calculations and experiments reveals that the significant creep deformation arises from the rapid absorption of high density dislocations stored in the loading regime. Our experiments imply that stored dislocations during loading are highly unstable and dislocation activity can proceed and lead to significant post-loading plasticity.

Nanoindentation creep deformation behaviour of high nitrogen nickel-free austenitic stainless steel

“…As stated in previous papers [21,33,34], the dislocation structures formed in the loading regime are highly unstable. These dislocations can break down easily in the holding regime due to the sudden change of the deformation mode or the suddenly taken away of the continuous supporting of loading rate under the constant load [21,33,34].…”

“…As stated in previous papers [21,33,34], the dislocation structures formed in the loading regime are highly unstable. These dislocations can break down easily in the holding regime due to the sudden change of the deformation mode or the suddenly taken away of the continuous supporting of loading rate under the constant load [21,33,34]. Because that the stress still persists at a relatively high state in the initial holding regime, the activities of dislocations would not cease and these highly mobile dislocations can still continue to move forward and contribute to the plastic strain, i.e.…”

“…Because that the stress still persists at a relatively high state in the initial holding regime, the activities of dislocations would not cease and these highly mobile dislocations can still continue to move forward and contribute to the plastic strain, i.e. the nanoindentation creep strain [14,33,34]. Meanwhile, because that the stress condition in the initial holding regime can be still satisfied well with the dislocation nucleation, the newly activated dislocations are able to continue to nucleate and to produce the plastic strain further [14,33,34].…”

“…the nanoindentation creep strain [14,33,34]. Meanwhile, because that the stress condition in the initial holding regime can be still satisfied well with the dislocation nucleation, the newly activated dislocations are able to continue to nucleate and to produce the plastic strain further [14,33,34].…”

Effects of cold rolling deformation on microstructure, hardness, and creep behavior of high nitrogen austenitic stainless steel

“…The stored dislocations can propagate forward and produce plastic strain (i.e., the creep strain) when they are absorbed by GBs and TBs. [37,38] This indicates that the creep process observed above is mediated mainly by the activity of dislocations. In the initial holding regime, the dislocation structures will relax rapidly and a high internal stress will thus drop off.…”