Ultrasonic impact treatment (UIT) uses ultrasound to enhance the mechanical and physical properties of metals.[39] It is a metallurgical processing technique in which ultrasonic energy is applied to a metal object. Ultrasonic treatment can result in controlled residual compressive stress, grain refinement and grain size reduction. Low and high cycle fatigue are enhanced and have been documented to provide increases up to ten times greater than non-UIT specimens.
Depending on the desired effects of treatment a combination of different frequencies and displacement amplitude is applied. These frequencies range between 25 and 55 kHz,[41] with the displacement amplitude of the resonant body of between 22 and 50 µm (0.00087 and 0.0020 in)
