Effect of temperature compensation on properties and interfacial structure evolution of Al/CFRTP ultrasonic welded joints

5052 Al and carbon fiber-reinforced polyamide 6 composite (CF-PA6) were jointed via ultrasonic welding with the assistance of temperature compensation device. The effects of the ultrasonic welding time and temperature compensation on the microstructure and mechanical properties of the joints were investigated. Through analysis of the wettability and fluidity of the molten carbon fiber-reinforced thermoplastic composites (CFRTP), the bonding mechanism and failure path of Al/CFRTP were clarified. The results show that under the conditions of temperature compensation of 220 °C and welding time of 1500 ms, the joint strength of the two components reaches 2480.4 N, which is 813.6% higher than that of Al/CFRTP components obtained at room temperature. Overall, temperature compensation prolonged the wetting time of molten CFRTP on the aluminum alloy surface. When the fluidity and wettability were coordinated with each other, a high-quality joint was formed. In addition, the ultrasonic welding process of Al/CFRTP mainly relies on “physical adsorption,” “diffusion effect,” and “mechanical locking effect” to achieve sufficient bonding, and the effect of hydrogen bonding is weak.