Effect of Tool Pin Eccentricity on the Microstructure and Mechanical Properties of Friction Stir Processed Al-6061 Alloy
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JMEPEG https://doi.org/10.1007/s11665-019-04025-y
Effect of Tool Pin Eccentricity on the Microstructure and Mechanical Properties of Friction Stir Processed Al-6061 Alloy Yu Chen, He Wang, Hua Ding, Jingwei Zhao, Fenghe Zhang, and Zhaohui Ren (Submitted August 1, 2018; in revised form November 22, 2018) Three different stir tools with the pin eccentricity of 0, 0.4 and 0.8 mm were applied to the friction stir processing (FSP) of Al-6061 alloy. Results show that the pin-affected zone (PAZ) enlarges and the grain size in the stir zone (SZ) decreases as the pin eccentricity increases. Moreover, the low peak FSP temperature induced by the pin eccentricity gives rise to the coarsening of strengthening precipitates in the SZ. Compared with the pin-eccentric FSP samples, the SZ produced without pin eccentricity exhibits the highest hardness and yield strength due to the high amount of fine precipitates. However, the application of pin eccentricity elevates the overall tensile properties of FSP samples through changing the failure location from heat-affected zone (HAZ) to SZ. Keywords
aluminum alloy, friction stir processing, mechanical properties, microstructure, pin eccentricity
1. Introduction Friction stir processing/welding (FSP/FSW) is widely applied in the processing/joining of aluminum alloys (Ref 1). It is well known that the stir tool plays an important role in affecting the properties of stir zone (SZ) (Ref 2). A suitable stir tool induces sufficient material flow in the SZ, which avoids the processing/welding defects and obtains satisfying quality of SZ (Ref 3). Nowadays, the designation of stir tool, especially stir pin, becomes more and more complex. And a lot of pin profiles have been exploited, such as tapered octagonal, straight hexagonal, threaded cylindrical and triangular (Ref 4-6). However, the above complex profiles are relatively difficult to fabricate, and moreover, these complex profiles are easy to get worn during FSW/FSP. The fabricating cost of stir tool will be increased as the life of stir tool is shortened. Therefore, the designation of pin profile should be as simple as possible on the premise of ensuring the quality of processing/welding. Recently, Elangovan et al. (Ref 5, 6) used stir tools with different pin profiles to friction stir weld AA2219 and AA6061 aluminum alloys and found that the pulsation stir behavior induced by the pin was beneficial for strengthening the SZ, and the pulsation stir behavior was mainly related to the pin eccentricity. Therefore, applying simple tool geometry with pin Yu Chen, Fenghe Zhang, and Zhaohui Ren, School of Mechanical Engineering and Automation, Northeastern University, Shenyang 110819, PeopleÕs Republic of China; He Wang and Hua Ding, School of Materials Science and Engineering, Northeastern University, Shenyang 110819, PeopleÕs Republic of China; Jingwei Zhao, School of Mechanical, Materials, Mechatronic and Biomedical Engineering, University of Wollongong, Wollongong 2522, Australia. Contact e-mail: [email protected].
Journal of Materials Engineering
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