Abnormal dislocation substructure in the ultrasonically welded joints of Cu single crystals

Abstract

Ultrasonic metal welding is a rapid bonding technology that combines ultrasonic softening and high-frequency friction. However, the massive dislocation proliferation in high-strain-rate deformation is contradictory to rapid dynamic recovery induced by the ultrasonic vibration. To investigate the contribution of ultrasonic to the joint microstructure, the Cu single crystals with [001], [101], [111] orientations were selected to trace the abnormal deformation microstructure. It was indicated that the ultrasonic excitation broke the correlation between geometrically necessary boundaries and grain orientation, which resulted in a similar micro-hardness in the range of 112.5–116.0 HV near the interface in three single crystal joints. An analytical model of interfacial friction deformation was proposed to prove the abnormal enlargement of dislocation cells under ultrasonic excitation.

KEYWORDS:

• Ultrasonic welding
• copper single crystal
• dislocation structure
• transmission Kikuchi diffraction

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [NSFC 52175310]. A part of the work was also supported by the National Science and Technology Major Project [2017-VI-0009-0080], the Guangdong Province key research and development program [2019B010935001], and the Shenzhen Science and Technology Plan [Project No. GXWD20201230155427003-20200821172456002].