Initiation, evolution, and saturation of coupled grain boundary motion in nanocrystalline materials

P Wang and XH Yang and D Peng, COMPUTATIONAL MATERIALS SCIENCE, 112, 289-296 (2016).

DOI: 10.1016/j.commatsci.2015.10.049

Coupled grain boundary (GB) motion in sheared nanocrystalline materials composed of Ni, Al, or Cu is investigated by atomistic simulation methods, and the effects of grain size and temperature are evaluated. Due to the pinning effect of triple junctions, saturation of coupled GB motion is observed in all the nanocrystals except Cu. The two components of coupled GB motion, normal migration (NM) and tangential motion (TM), initiate and saturate at nearly equivalent nominal shear strains. Accompanied with coupled GB motion, massive dislocations and stacking faults are found to form within some grains, and the elementary structure units in the observed GBs transform from in-order to out-of- order. Compared with nanocrystalline Ni, the coupled GB motion in nanocrystalline Al has a reduced shear strain threshold and saturated NM displacement. The effects of grain size and temperature are similar in both NM and TM, so that their influence on coupled GB motion is slight. (C) 2015 Elsevier B.V. All rights reserved.

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