Superplastic Behavior of Micro-regions in Two-pass Friction Stir Processed 7075Al Alloy


Effect of overlapping passes on the microstructure and superplastic behavior of friction stir processed (FSP) 7075Al was subjected to a detailed investigation. Overlapping passes exerted no obvious effect on the size of recrystallized grains. Both single and two-pass FSP 7075Al exhibited similar grain sizes of 5.4-5.7 μm. Compared to single-pass FSP, two-pass FSP resulted in an enhancement in superplastic elongation and a change in superplastic response. A shift to higher optimum temperature was observed in the two-pass FSP 7075Al. Furthermore, overlapping passes led to a shift to higher optimum strain rate in the center region of second pass in the two-pass FSP 7075Al. Maximum superplastic elongation of 1220% was achieved at 480 °C and an initial strain rate of 1 × 10−2 s−1 in the center region of second pass in the two-pass FSP 7075Al. Analyses of superplastic data indicated that grain boundary sliding is the main superplastic deformation mechanism for both single and two-pass FSP 7075Al.


Materials Science and Engineering


Hundred Talents Program of Chinese Academy of Sciences
National Natural Science Foundation (China)
National Outstanding Young Scientist Foundation
National Science Foundation (U.S.)
University of Missouri Research Board

Keywords and Phrases

Friction Stir Processing; Overlapping; Aluminum alloys; Superplasticity

Document Type

Article - Journal

Document Version


File Type





© 2009 Elsevier, All rights reserved.