ISSN: 1003-6326
CN: 43-1239/TG

Vol. 31    No. 12    December 2021

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Effect of welding speed on microstructure and mechanical properties of Al-Mg-Mn-Zr-Ti alloy sheet during friction stir welding
Tian DING1,2, Hong-ge YAN1,2, Ji-hua CHEN1,2, Wei-jun XIA1,2, Bin SU1,2
(1. School of Materials Science and Engineering, Hunan University, Changsha 410082, China;
2. Hunan Provincial Key Laboratory of Spray Deposition Technology & Application, Hunan University, Changsha 410082, China
Abstract: Effects of welding speed on the microstructure evolution in the stir zone (SZ) and mechanical properties of the friction stir welding (FSW) joints were studied by OM, XRD, SEM, TEM, EBSD and tensile testing. Compared with the base metal (BM), an obviously fine dynamic recrystallization (DRX) microstructure occurs in the SZ and the DRX grain size decreases from 5.6 to 4.4 mm with the increasing of welding speed. Fine DRX microstructure is mainly achieved by continuous dynamic recrystallization (CDRX) mechanism, strain induced boundary migration (SIBM) mechanism and particle stimulated nucleation (PSN) mechanism. Meanwhile, the geometric coalescence and the Burke-Turnbull mechanism are the main DRX grain growth mechanisms. Among all the welding speeds, the joint welded at rotation speed of 1500 r/min and welding speed of 75 mm/min has the greatest tensile properties, i.e. ultimate tensile strength (UTS) of (509±2) MPa, yield strength (YS) of (282±4) MPa, elongation (El) of (23±1)%, and the joint efficiency of 73%.
Key words: friction stir welding; mechanical properties; dynamic recrystallization; nucleation mechanism; grain growth mechanism
Superintended by The China Association for Science and Technology (CAST)
Sponsored by The Nonferrous Metals Society of China (NFSOC)
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