Effect of Tool Pin Eccentricity on the Microstructure and Mechanical Properties of Friction Stir Processed Al-6061 Alloy
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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.
Keywordsaluminum alloy friction stir processing mechanical properties microstructure pin eccentricity
The present study is financially supported by the Fundamental Research Funds for the Central Universities of China (Nos. N172410002-03, N180303029) and the Nature Science Foundation of Liaoning Province (No. 20180550058). Besides, one of the authors, Zhaohui Ren, gratefully acknowledges the financial supports from the National Science Foundation of China (No. 51475084) and National Support Program, National Key Research and Development (No. 2017YFB1103700).