Improving tensile-shear properties of friction stir lap welded dissimilar Al/Mg joints by eliminating hook defect and controlling interfacial reaction

作者：Mao, Yuqing^*; Yang, Ping; Zhang, Wenyan; LI, Ning; Nie, Hao; Lin, Danyang; Ke, Liming

来源：Chinese Journal of Aeronautics, 2023, 36(7): 257-267.

DOI：10.1016/j.cja.2022.11.026

• Dissimilar Al
• Mg alloys
• Friction stir lap welding
• Hook defect
• Interface microstructure
• Tensile-shear properties

To improve tensile-shear properties of fiction stir lap welded (FSLW) dissimilar Al/Mg joints, pin-tip profiles were innovatively designed and welding speed was optimized, and effects of them on formation, interface microstructure and mechanical properties of different FSLW joints were investigated. With increasing the welding speed, the tensile-shear load of FSLW joints pro-duced by three pins presents an increasing firstly and then decreasing trend. Compared with R-pin, the hook and hole defect in the joints made by S-pin and T-pin are eliminated owing to addi-tional eccentric force. Moreover, the joints obtained by T-pin at 75 mm/min have the highest tensile-shear load, and a maximum value of 3.425 kN is produced, which increases by 96.8%. Meanwhile, the pin-tip profile improves significantly the interface reaction depending on the weld-ing temperature. For R-pin, thick brittle intermetallic compounds of about 6.9 lm Al3Mg2 and 13.3 lm Al12Mg17 layers at the welding interface derived from diffusion reaction are formed, result-ing in continuous cracks. However, using T-pin can raise the interface temperature, and which makes the interface liquefy locally to generate only 2.2 lm Al3Mg2 layer and dispersive (Al12- Mg17 + Mg) eutectic structure. This can release high residual stress and remove welding crack, con-sequently enhancing the interface properties of T-pin joints.& COPY; 2022 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

• 单位
  南昌航空大学