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    Review of 'The Mechanism of Ultrasonic Vibration on Grain Refining and Degassing in GTA Spot Welding of Copper Joints'

    The Mechanism of Ultrasonic Vibration on Grain Refining and Degassing in GTA Spot Welding of Copper JointsCrossref
    Vibration effect on the microstructural and mechanical aspects of copper GTA spot weldment
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    The Mechanism of Ultrasonic Vibration on Grain Refining and Degassing in GTA Spot Welding of Copper Joints

    This paper examines the effect of ultrasonic vibration (USV) on grain size and interrupted porosity in Gas Tungsten Arc (GTA) spot-welded copper. Grain size was refined by perpendicularly attaching a transducer to the welded sheet and applying USV to the weld pool for a short time (0, 2, 4, and 6 s) in addition improvements to the degassing process. Results illustrate a significant reduction of grain size (57%). Notably, USV provided interaction between reformations (fragmentation) and provided nucleation points (detaching particles from the fusion line) for grains in the nugget zone and the elimination of porosity in the nugget zone. The GTA spot welding process, in conjunction with USV, demonstrated an improvement in the corrosion potential for a copper spot-welded joint in comparison to the joint welded without assistance of USV. Finally, welding of copper by GTA spot welding in conjunction with ultrasound for 2 s presented significant mechanical properties.

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      This work has been published open access under Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Conditions, terms of use and publishing policy can be found at www.scienceopen.com.

      corrosion,copper,tensile shear strength,gta spot welding,grain refinement,degassing

      Review text

      • The market requirements of copper grow annually due to the weight and strength factor, in addition to the electrical conductivity, especially for electrical applications. The copper alloys can be spot welded for electrical applications. In addition to be used in structural connections in hybrid cars. In this work, the effect of ultrasonic vibration (USV) on the microstructures and the mechanical properties of spot welded copper has been studied. The effect of vibration time on the degassing processes, porosity distributions, and corrosion rate have been presented.
      • The porosity in the nugget zone (NZ) of a pure copper-welded joint reduces the electrical conductivity. Therefore, USV was used to reduce the porosity and refine the nugget zone. The increasing the vibration time will reduce the porosity.
      • Abaqus CAE software was used to simulate the fracture mechanics of spot welding of copper joints.
      • The fracture type was investigated. The increasing of the nugget diameter from 5 to 10 mm will change the fracture type from interfacial fracture to pullout fracture. In my opinion, the increasing of the weld nugget will increase the weld penetration through the sheet thickness. Hence, the pullout fracture is always dominated for high-penetrated nugget. Tensile shear testing specimen have been used. However, tensile peel test can also be used for pure tension. Therefore, the author may investigate the effect of porosity distribution on the tensile strength of the peel specimens.
      • For welded joints without USV, the heat dissipation from the nugget zone toward the HAZ, will increase the grain size. But for 6 second of USV, the grain size in nugget zone will be refined due to the increasing of the cooling rate.
      • On the other hand, the increase of USV to 6 s showed a decrease of peak load and strength, in which several micro-solidification cracks appeared in the fusion zone. Because, the increasing of the USV time to 6 second will produce micro-solidifications cracks in the fusion zone or in the weld nugget due to the increasing of the cooling rate. Hence, decreasing peak load and strength.
      • The formation of H2O steam bubbles in the form of porosity at the fusion line formed a microporosity that may have reduced the electrical conductivity of the copper joint.
      • The improvement of electrical conductivity was attributed to the use of a fillerless process and the degassing of porosity away from the nugget zone. Hence, improving the corrosion behavior.
      • Complete FE model is recommended to show the side of crack initiation. 
      • In addition, USV during the welding time can be studied. In my opinion, it has a significant effect.


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