Abstract
The influence of 20 kc/s ultrasound on precipitation-hardening kinetics in a copper-beryllium alloy has been investigated. Half-wavelength specimens were employed so that a resonant standing wave existed. The ultrasonically irradiated specimens were subjected to a maximum acoustic-stress amplitude of 3.5 × 108 dynes/cm2 (5100 lb/in2). Acoustic energy brought about a small acceleration of the precipitation rate, the increase in overall ageing kinetics being caused by acoustic enhancement of the grain-boundary precipitation reaction. Ultrasonic energy did not significantly change the apparent activation energy for precipitation or alter the time-dependence of the rates of precipitate nucleation and growth.
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