Investigations on the material property changes of ultrasonic-vibration assisted aluminum alloy upsetting

Numerous studies have shown the benefit of ultrasonic-vibration assisted metal forming. This benefit include a reduction in forming forces, which might be attributed to the superposition of stress, increased temperatures, the effects of interface friction, and energy absorption of dislocation. This study conducts a series of experiments and analyses to investigate the main mechanisms of a reduction in forming forces during ultrasonic-vibration assisted A6061-T6 aluminum alloy upsetting.The findings of this research confirm that, under frictionless conditions, ultrasonic vibration still reduced forming forces, and ultrasonic vibration can increase the temperature of specimens and soften specimen surface during upsetting. From metallographic analyses and micro-hardness tests, the results reveal that energy absorption of dislocation was occurred during upsetting, which also contribute to the reduction of forming force.This research concludes that the mechanisms of increased temperatures and energy absorption of dislocation can affect the material property and make a reduction in forming forces; however, the interface friction effect has nothing to do with a reduction in forming forces.

► The mechanisms of ultrasonic-vibration assisted upsetting were identified. ► Ultrasonic can reduce the material’s flow stress when friction is negligible. ► Metal can absorb energy through heat energy, making a reduction in forming force. ► The grains have been refined when the ultrasonic-vibration is superimposed. ► The motions of dislocation were occurred, making a reduction in forming forces.