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

Abstract

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.

Mitigation of Porosity and Residual Stress on Carbody Aluminum Alloy Vibration Welding: A Systematic Literature Review

“…Figure 8 shows the percentage of porosity area in the welded and unaided cross-section of the USV [66]. Vibration welding is able to reduce porosity [47] because of the movement and movement of gas from the bottom to the surface of the weld pool during the compaction process [67].…”

“…Vibration welding can reduce porosity due to an increase in heat dissipation. With vibration it will increase the internal pressure, so that trapped hydrogen bubbles will move up to the surface of the molten metal and escape [66].…”

“…According to [66], the internal pressure that occurs (Pa) on the molten weld metal due to ultra-Figure 8. The distribution of porosity from bottom to top surfaces in GTA spot-welded joints with and without vibration assistance [66] sonic vibrations so that bubbles rise to the surface of the molten metal is expressed by Equation ( 2).…”

“…The application of vibration during welding is also able to significantly reduce the peak temperature of the HAZ due to rapid cooling [66] as shown in Figure 13a. The peak temperature in the HAZ reaches 565 °C when welding without USV.…”

“…Figure 5. (a) The microstructure of the BM; and (b) the grain size and aspect ratio for GTA spot-welded copperjoints with different USV times[66] …”