Abstract

Deformed coarse-grained polycrystalline metals always unload elastically where permanent dislocation network well-developed in the loading regime hinders the movement of dislocations and allows only the elastic relaxation of stress. Such elastic unloading behavior is, however, unexpected in nanocrystalline metals because the dislocation network cannot effectively form inside nanometer-scale grains. In this work, we report the experimental finding of significant plastic deformation that emerges in the unloading regime in the compressive cyclic test at room temperature of nanocrystalline Cu. The magnitude of plastic strain produced during unloading depends strongly on loading and unloading rates. This plastic unloading behavior arises from the rapid absorption of dislocations accumulated during loading, which was quantitatively interpreted by performing the incremental unloading test and developing a relationship between the dislocation density and the loading and unloading rates based on the models of the statistical absorption of dislocations by grain boundaries and the dislocation emission from grain boundary ledges. Concurrently, the evolution of deformation structures during the cyclic deformation was also analyzed in terms of the interactions of gliding dislocation–twin boundaries.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.