The Influence of Ultrasound on the Kinetics of Recrystallization in Copper

The influence of 20 kHz acoustic oscillations on the recrystallization kinetics of oxygen-free, high-conductivity copper has been investigated. Resonance standing waves with a maximum acoustic stress amplitude of 3.2 × 108 dyn/cm² (4640lbf/in²) were developed in half-wavelength-long specimens. Ultrasound caused a great increase (30–100 times) in the recrystallization rate, the degree of acoustic enhancement being proportional to the acoustic stress amplitude. Ultrasound did not alter the form of the time-dependence of the nucleation and growth rates for recrystallization, but did decrease the apparent activation energy for recrystallization from 31.5 kcal/mol (132 kJ/mol) (without acoustic energy) to 17.0 kcal/mol (71 kJ/mol).