The defining role of ultrasonic on the relaxed GBs and superior thermal stability of copper coatings.

The nanostructured Cu coatings were electrodeposited with different vibration, such as vibration-free, agitation and ultrasonic.Ultrasonic could help to refine grains and optimize the comprehensive performance of the coating. The effect of vibration on the thermal stability of pure Cu coatings was investigated with the coatings annealing at 450 °C, 500 °C and 550 °C. Both agitation and ultrasonic can suppress the nanograins coarsening and the effect of ultrasonic was more excellent. Ultrasonic can not only increase the content of nanotwins and triple junctions but also induce the relaxation of GBs. Therefore, the ultrasonic deposited nanograins in the low-energy state exhibit superior thermal stability. The mechanisms of the thermal stability in the electrodeposited coatings were studied from thermodynamics and dynamics. By comparing dislocation density, stacking faults energy and grain boundaries energy, it was proved that the driving force of grain growth in the ultrasonic deposited coating was lowest. Both the methods of isothermal measurements and Kissinger showed that the ultrasonic could increase the activation energy of grain growth to inhibit grain boundary mobility. • The ultrasonic deposited nanograins annealed at 550 °C for 3600 s only grew from 29.4 nm to 178.7 nm. • Ultrasonic cavitation promoted the formation of nanotwins and relaxation of GBs. • Ultrasonic reduced driving force of grain growth and GBs mobility effectively by analysis of thermodynamics and dynamics. • Electrodeposition combining with ultrasonic provided an important route to stabilize nanomaterials without alloying. [ABSTRACT FROM AUTHOR]