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<p>The friction stir spot welding (FSSW) technique is a significant alternative to single-point joining techniques in traditional welding such as resistance spot welding and riveting because it shows great potential. Thus, the FSSW technique was used to produce spot-welding lap joints of dissimilar Cu-S355JR sheets with 2&#xa0;mm thickness. To examine the effect of FSSW conditions on the mechanical and metallurgical characteristics of the welded samples, various dwell times of 2.5, 5, 7.5, 10, and 12.5&#xa0;s employed a fixed rotating speed of 1500&#xa0;rpm. For metallurgical characterization, optical microscopy, and SEM have been employed. Concurrently, the tensile-shear test and Vickers hardness test were used to assess the mechanical characteristics of the dissimilar FSSWed Cu-S355JR lap joints. According to the experimental results, an improvement in thermal distribution showed a larger bonding area between the interface for Cu and steel sheets and attained sound joints with a dwell time increased from 2.5 to 12.5&#xa0;s. As a result, the peak temperature increased with increasing dwell time in the thermal cycle that was recorded during the FSSW. Moreover, a mixture of grain microstructures of Cu and steel phases (pearlite and α-ferrite) was formed in the interface through the diffusion process during FSSW as a result of an interaction that occurred between the bottom sheet of steel and the Cu top sheet in the stir zone (SZ). The joint formation and form of the hook area benefited somewhat from increased dwell times, which raised the maximum-shear load and microhardness values of the samples. Also, for all welded joints at dwell times ranging from 2.5 to 12.5&#xa0;s, the fracture mechanism showed that the interface was completely sheared off after the tensile shear test. Finally, the FSSW is an attractive novel technique for optimizing the welding conditions used to join Cu-S355JR dissimilar materials that are widely employed in various industrial fields, including nuclear and automotive industries.</p>

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Effect of dwell time on mechanical and metallurgical behavior of dissimilar FSSWed Cu-S355 JR lap joints

  • 期刊论文

  • 发表日期：

    2025年4月23日

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  • Mohamed Fouad Rabea,
  • Ramy A. Fouad,
  • Mohamed M. El-Sayed Seleman,
  • Essam Ahmed

摘要

The friction stir spot welding (FSSW) technique is a significant alternative to single-point joining techniques in traditional welding such as resistance spot welding and riveting because it shows great potential. Thus, the FSSW technique was used to produce spot-welding lap joints of dissimilar Cu-S355JR sheets with 2 mm thickness. To examine the effect of FSSW conditions on the mechanical and metallurgical characteristics of the welded samples, various dwell times of 2.5, 5, 7.5, 10, and 12.5 s employed a fixed rotating speed of 1500 rpm. For metallurgical characterization, optical microscopy, and SEM have been employed. Concurrently, the tensile-shear test and Vickers hardness test were used to assess the mechanical characteristics of the dissimilar FSSWed Cu-S355JR lap joints. According to the experimental results, an improvement in thermal distribution showed a larger bonding area between the interface for Cu and steel sheets and attained sound joints with a dwell time increased from 2.5 to 12.5 s. As a result, the peak temperature increased with increasing dwell time in the thermal cycle that was recorded during the FSSW. Moreover, a mixture of grain microstructures of Cu and steel phases (pearlite and α-ferrite) was formed in the interface through the diffusion process during FSSW as a result of an interaction that occurred between the bottom sheet of steel and the Cu top sheet in the stir zone (SZ). The joint formation and form of the hook area benefited somewhat from increased dwell times, which raised the maximum-shear load and microhardness values of the samples. Also, for all welded joints at dwell times ranging from 2.5 to 12.5 s, the fracture mechanism showed that the interface was completely sheared off after the tensile shear test. Finally, the FSSW is an attractive novel technique for optimizing the welding conditions used to join Cu-S355JR dissimilar materials that are widely employed in various industrial fields, including nuclear and automotive industries.