Integrated Analysis of Temperature, Vibration, and Metallurgical Characteristics in Ultrasonic Welding of 6061-T6 Aluminum Alloy

Abstract

This study investigates the ultrasonic welding (UW) of 6061-T6 aluminum alloy to analyze the interrelation between thermal input, vibration behavior, and metallurgical characteristics under varying welding conditions. Real-time measurements of heat generation and upper sheet displacement were obtained using a non-contact infrared temperature and laser displacement sensors. The sensor data were correlated with tensile-shear testing and hardness measurements, and microstructural analysis conducted through optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD).The results demonstrated that increasing welding time led to greater heat generation and more pronounced plastic flow at the weld interface, while excessive applied pressure reduced material displacement and frictional heating, thereby suppressing plastic deformation. Despite reduced microstructural flow at high pressures, improved mechanical strength was observed, indicating that bonding strength is governed by both frictional plastic flow and pressure-induced compaction. Furthermore, EBSD analysis revealed that fine recrystallized grains were more widely distributed with increased weld time, particularly in the upper sheet, due to localized thermal effects. In addition, vibration amplitude measurements of the upper sheet showed that displacement decreased from approximately 60 mu m at 2 bar to 36 mu m at 3 bar, suggesting that higher pressure restricted ultrasonic energy transmission and reduced material flow.Temperature and vibration trends measured during welding provided reflected interfacial bonding behavior, suggesting its potential for in-line weld quality prediction. This integrated approach offers a comprehensive understanding of ultrasonic welding mechanisms and presents a framework for sensor-based monitoring and optimization of weld quality in aluminum alloy applications.