Molecular dynamics simulation-based study of creep-ratcheting behavior of nanocrystalline aluminum

PN Babu and CS Becquart and S Pal, APPLIED NANOSCIENCE, 11, 565-581 (2021).

DOI: 10.1007/s13204-020-01595-5

In the present study, molecular dynamics simulations have been performed to investigate the creep-ratcheting deformation behavior of nanocrystalline aluminum (NC Al) having an average grain size of similar to 8 nm. The influence of deformation temperature on creep-ratcheting behavior has been studied and associated with underlying mechanisms based on the structural evolution of the material identified. The vacancy concentrations, strains and dislocation densities have been evaluated at the end of each stage of creep-ratcheting process for two ratcheting stress ratios and three different temperatures. In the mean time, the microstructural and defect evolution has been investigated. Accumulation of creep-ratcheting strain is found to increase with the deformation temperature in the range of temperature investigated: 10-467 K. Cyclic hardening dominates in the initial stages of creep-ratcheting, whereas cyclic softening dominates in the final stages at a higher temperature. The creep-ratcheting plots exhibit a primary and steady state regions at room temperature (300 K). In addition, a tertiary region is also perceived at high temperature (467 K). The NC Al specimen is also found to be damaged earlier at a higher temperature (i.e., 467 K) than at 10 K and 300 K. The highest dislocation density is attained for room temperature creep-ratcheting deformation. Finally, it is seen from the dislocation analysis that the Shockley partial and full dislocations are the driving dislocations for the creep-ratcheting deformation process.

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