Grain refiners are currently used in casting aluminum alloys to reduce the grain size and to produce equiaxed grains during solidification of the alloys. Using inoculants to refine grains makes alloys castable but produces several disadvantages, including particle agglomerates, local defects, and impurities. In contrast, ultrasonic vibrations can be used in the place of grain refiners to refine grains without the disadvantages of using inoculants. In this study, high intensity ultrasonic vibrations were applied during solidification of pure aluminum. The grains of pure aluminum treated using ultrasonic vibrations were compared to the grains obtained using the TiB2 grain refiner. It was found that the grain size in the pure aluminum ingots subjected to ultrasonic vibrations was comparable to those with the addition of grain refiners.