Microstructure and Mechanical Properties of TIG and Friction Stir Welded Joints of Sc-contained High Strength Aluminum Alloy Sheet

doi:10.3901/JME.2020.06.221

Abstract

Abstract: 3 mm thick Al-Zn-Mg-Cu-Sc alloy plates were subjected to tungsten inert gas welding (TIG) and friction stir welding (FSW), respectively. The microstructure and mechanical properties of the TIG and FSW joints were investigated. The results showed that defect-free joints of both TIG and FSW were acquired. For the TIG joint, the nugget zone (NZ) was characterized with coarsened grains, the hardness distribution exhibited “M” shape with low hardness value in the center (～125 HV), and the lowest hardness zone (LHZ, ～110 HV) located in the heat affected zone (HAZ); the ultimate tensile strength (UTS) of 417 MPa was obtained, ～71% of the BM. For the FSW joints, the NZs were characterized with exquiaxed fine grains, and the grain sizes decreased with increasing the welding speed; the hardness distribution presented “W” shape with the LHZ located in the HAZ (～115 HV). FSW joints with high strength could be obtained under the rotation rates of 400-1 200 r/min, and the highest UTS of 458 MPa was achieved under the rotation rate of 1 200 r/min and welding speed of 200 mm/min, ～79% of the BM. When the welding speed was too fast, defects were likely to appear in the NZs due to the poor deformation ability of the alloy, resulting in the premature failure of tensile samples in the center of the NZs.

Key words: high strength aluminum alloy, TIG welding, friction stir welding, microstructure, mechanical properties

CLC Number:

TG456

YANG Chao, WANG Yingjun, XU Yanli, CAI Jing, YU Baohai, NI Dingrui. Microstructure and Mechanical Properties of TIG and Friction Stir Welded Joints of Sc-contained High Strength Aluminum Alloy Sheet[J]. Journal of Mechanical Engineering, 2020, 56(6): 221-228.

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