Quantitative Measurements of Grain Boundary Sliding in an Ultrafine-Grained Al Alloy by Atomic Force Microscopy |
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Authors: | Jung H Han Farghalli A Mohamed |
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Affiliation: | (1) Department of Chemical Engineering and Materials Science, University of California—Irvine, Irvine, CA 92697-2575, USA; |
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Abstract: | In the current study, quantitative measurements for grain boundary sliding (GBS) in ultrafine-grained (UFG) 5083 Al by atomic
force microscopy (AFM) were performed. An ion beam polishing and etching technique was used to reveal grain boundaries in
the alloy for AFM characterization. A comparison between the average grain sizes measured from AFM images and those estimated
from transmission electron microscopy micrographs and electron backscatter diffraction (EBSD) maps showed excellent agreement.
The vertical offset of GBS was measured by comparing predeformation and postdeformation AFM images. By analyzing these measurements,
the contribution of GBS to the total tensile strain in 5083 Al was estimated as 25 pct at a strain rate of 10−4 seconds−1 and a temperature of 473 K (200 °C). It was demonstrated that the relatively low value of the contribution of GBS to the
total strain is most likely the result of testing UFG 5083 Al under experimental conditions that favor the dominance of region
I (low-stress region) of the sigmoidal behavior characterizing high-strain-rate superplasticity, which was reported previously
for the alloy. |
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