Effect of Welding Speed on Mechanical Properties and the Strain-Hardening Behavior of Friction Stir Welded 7075 Aluminum Alloy Joints
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The effect of welding speed on the microstructural evolution, mechanical properties and strain-hardening behavior of friction stir welded (FSWed) high-strength AA7075-T651 was investigated. Large intermetallic particles and grains, whose sizes increased at lower welding speeds, were present in the heat-affected zone. FSWed joints fabricated at the higher welding speed or lower strain rates exhibited higher strength, joint efficiency and ductility than those fabricated at lower welding speeds or higher strain rates. A maximum joint efficiency of 97.5% and an elongation to failure of 15.9% were obtained using a welding speed of 400 mm/min at a strain rate of 10−5 s−1. The hardening capacity, strain-hardening exponent and strain-hardening rate of the FSWed joints were significantly higher than those of the base material, but materials exhibited stage III and stage IV hardening characteristics. The results morphology of the fracture surfaces is consistent with the above results.
Keywords7075 aluminum alloy friction stir welding mechanical properties strain-hardening behavior
The authors gratefully acknowledge the financial support of the project from the National Natural Science Foundation of China (No. 51405392), Specialized Research Fund for the Doctoral Program of Higher Education (No. 20136102120022), and Fundamental Research Funds for the Central Universities (No. 3102015ZY023), Hong Kong Scholar Program (No. XJ2016043).
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