Observations of crystal orientation of pure aluminum damaged by cavitation impact

Abstract

The effect of cavitation impact on pure aluminum that is almost single crystal was investigated from a crystallographic point of view. Cavitation erosion was generated in water by an ultrasonic vibrating horn. After the experiment, the cross-section of the specimen was observed by electron backscattering diffraction technique. Grain boundaries, crystal directions and local changes of crystal direction were estimated. As a result, it was found that cavitation impact induces grain refining of grains and that the kernel average misorientation (KAM) value in the grain increases through the impact until grain refining occurs, but the KAM value is reset after grain refining. From these observations, a grain refining mechanism is proposed so that the grain refining is like a phase transition where deformation energy in a grain accumulated by cavitation impact is rearranged as grain boundary energy of refined grains.