Abstract
Heart treatments with an ultrasonic vibration has been carried out for microstructural control in solid state materials. Post 60% cold-rolled aluminum specimens were subjected to the ultrasonic heat treatment at 573K, and changes of microstructures were analyzed by a FE-SEM/EBSP/OIM. The condition of the ultrasonic vibration used here was 48.5kHz in frequency, 1.5μm in displacement amplitude and 5.8MPa in stress amplitude. We found that the application of an ultrasonic vibration could enhance the recrystallization. Of particular interest is that the higher was vibration stress amplitude, the more occurred recrystallization. The OIM observation revealed that as the stress amplitude was increased, the recrystallized grains tended to be refined and to have a texture. The frequency of low energy boundaries increased as well. From the analogy of microstructural change by fatigue, the ultrasonic vibration stress would encourage the formation of dislocation cell structures. The rearrangement of dislocation structure by the ultrasonic vibration should contribute to enhancement of recrystallization.
